MDGx
 MS-DOS 5.00 - 8.00
Undocumented + Hidden Secrets

WinDOwS

Some of these UNDOCUMENTED MS-DOS commands might save your "computing life" one day, as they have saved mine.
I will post here ALL New DOS Secrets every time I'll also add them to SECRETS.TXT, part of my Updated ©Tricks + Secrets Files, FREEware:
• Windows 9x/NT4/2000/ME/XP/2003 + DOS 7.xx/8.00: W95-11D.EXE
• Windows/WfWG 3.1x + DOS 6.xx: W31-11D.ZIP

ALWAYS BACKUP ALL YOUR HARD DRIVES TO A SAFE LOCATION
BEFORE USING ANY TOOLS THAT MODIFY DISK STRUCTURE !

    CONTENTS: [alphabetical order]

    MUST HAVE: [99.99% FREE(ware)]

    MS-DOS Commands on the Internet:

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COMMAND.COM HIDDEN PARAMETERS

    COMMAND.COM is the MS-DOS mode command line interpreter, located by default in %winbootdir% + %winbootdir%\COMMAND (default is C:\WINDOWS + C:\WINDOWS\COMMAND) [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00], C:\DOS or C:\MSDOS [MS-DOS 5.00/6.xx]. Another copy of COMMAND.COM may exist in C:\ root.
    IMPORTANT: To become familiar with the COMMAND.COM command line switches (the documented ones anyway):All COMMAND.COM parameters listed below can be used on the CONFIG.SYS file SHELL= line (primary permanent shell):
    SHELL=C:\COMMAND.COM C:\ /E:512 /D /F /T /Z
    on a Windows PIF file (MS-DOS Prompt application) command line, in batch files, or/and at the plain DOS prompt (secondary shell, which can be made permanent if adding the /P switch).

    In MS-DOS 5.00 - 6.22 you can use this undocumented workaround to force COMMAND.COM to load "high", which requires an upper memory manager in CONFIG.SYS, like EMM386.EXE or UMBPCI.SYS. Example:
    SHELL=C:\COMMAND.COM /C LOADHIGH=C:\COMMAND.COM C:\ /E:512 /P
    This works ONLY IF:DISADVANTAGE: In some cases a second copy of COMMAND.COM remains resident in (upper) memory. :(
    More details.
    In MS-DOS 7.00 - 8.00 [a.k.a. Windows 95/98/ME] this function is built into IO.SYS, and COMMAND.COM loads in UMA (Upper Memory Area) automatically ONLY IF UMBs (Upper Memory Blocks) are provided by an upper memory manager like EMM386.EXE or UMBPCI.SYS, and IF the line "DOS=HIGH,UMB" exists in CONFIG.SYS.

  1. COMMAND /D [MS-DOS 5.00 and above ONLY]

    COMMAND /D (DENY) performs different actions depending on the MS-DOS version:
    • in MS-DOS 5.00: used on the CONFIG.SYS file SHELL= line prevents the execution of the AUTOEXEC.BAT file (if present) at bootup.
    • in MS-DOS 6.xx and 7.xx/8.00 [a.k.a. Windows 9x/ME]: disables the automatic disk "Fail" response if enabled by the /F (FAIL) parameter (see "COMMAND /F" below).

  2. COMMAND /F [MS-DOS 6.00 and above ONLY]

    COMMAND /F (FAIL) removes the "Abort, Retry, Fail" message and forces a "Fail" response to all "Abort, Retry, Fail" prompts issued by the DOS critical error handler. If the disk is not ready it automatically goes to "Fail".

  3. COMMAND /T [Windows 95 + MS-DOS 7.00 and above ONLY]

    COMMAND /T forces the COMMAND.COM resident module to load permanently in low memory (below the 640K barrier), even if the Upper Memory Area (UMA) is enabled by an upper memory manager (i.e. EMM386.EXE or UMBPCI.SYS) from CONFIG.SYS.
    Using /T in combination with the /P (PERMANENT) parameter, ONLY from the DOS prompt or in batch files (NOT from the CONFIG.SYS SHELL= line), also executes the AUTOEXEC.BAT file (if present), besides forcing the COMMAND.COM resident module to load permanently in low memory.
    WARNING: Using /T on the CONFIG.SYS SHELL= line may lock up Windows 9x/ME GUI upon shut down!

  4. COMMAND /Z [Windows 95 + MS-DOS 7.00 and above ONLY]

    COMMAND /Z (ZERO) displays the "ERRORLEVEL" return code messages after executing external DOS commands (internal DOS commands do not display error codes in this manner).
    You'll see a message like this when using the /Z parameter [errorlevel 0 is the default (normal) return code]:

    "Microsoft(R) Windows 98
    (C)Copyright Microsoft Corp 1981-1999.
    Return code (ERRORLEVEL): 0
    WARNING: Reloaded COMMAND.COM transient    "

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EMM386.EXE HIDDEN PARAMETERS

    EMM386.EXE is the Microsoft upper/extended/expanded memory manager, located by default in C:\WINDOWS [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00], C:\DOS or C:\MSDOS [MS-DOS 5.00/6.xx].
    EMM386.EXE can be loaded ONLY in CONFIG.SYS using the DEVICE command. Example:
    DEVICE=C:\WINDOWS\EMM386.EXE RAM I=B000-B7FF D=256 AUTO NOTR
    The EMM386.EXE DEVICE line MUST appear in CONFIG.SYS AFTER the HIMEM.SYS line, and BEFORE ANY other device drivers loaded with DEVICE, DEVICEHIGH, INSTALL or INSTALLHIGH.
    Running:
    EMM386
    from a DOS prompt, displays the EMM386 status.
    EMM386.EXE provides access to the Upper Memory Area (UMA), uses the computer's extended memory to simulate expanded memory and allows programs and device drivers to load into Upper Memory Blocks (UMBs).
    IMPORTANT: To become familiar with the EMM386.EXE command line switches (the documented ones anyway):

    DEVICE=drive:\path\EMM386.EXE NOTR [MS-DOS 6.00 and above ONLY]

    The EMM386.EXE default detection code searches for the presence of a Token Ring Network adapter, which may cause some computers to hang. In such cases use the NOTR parameter to disable this search.
    This is valid ONLY for EMM386.EXE versions 4.45 - 4.49 [MS-DOS 6.00 - 6.22] up to 4.95 [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00]. Example:
    DEVICE=C:\WINDOWS\EMM386.EXE NOTR

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FAT16 -> FAT32

    FAT16 [R.I.P.! :-)] is the most used File Allocation Table (FAT) 16-bit standard on "Wintel" PCs, recognized by all MS-DOS releases beginning with 4.00 (released back in 1991), and by all Windows versions.
    MS-DOS releases older than 4.00 used to operate with the obsolete FAT12 standard, discontinued, but still in use by the ol' floppy disk(ette) standard. :(
    FAT12 is [was :)] able to handle disk partitions only up to 16 MB using 4 KB clusters.

    FYI: Officially Microsoft implemented FAT16 only begining with MS-DOS 4.00 (through extended partitions larger than 32 MB), but unofficially FAT16 was already implemented in MS-DOS 3.3. FDISK.EXE supports extended partitions (the only way to take advantage of FAT16 at the time) begining with MS-DOS 3.3 (up to a total of 128 MB), but FORMAT.COM supports partitions larger than 32 MB only begining with MS-DOS 4.00. MS-DOS 3.3 FORMAT.COM supported partitions only up to 16 MB (FAT12), even if FAT16 was already available. :(
    Further reading: "Upgrading and Repairing PCs" book by Scott Mueller, second edition, page 653.
    [Thank you Mr. Nobby!]

    FAT16 limitations:

     Partition size  FAT16 Cluster size 
        0 -  127 MB  2 KB =  2048 B
      128 -  255 MB  4 KB =  4096 B
      256 -  511 MB  8 KB =  8192 B
      512 - 1023 MB 16 KB = 16384 B
     1024 - 2047 MB 32 KB = 32768 B

    In 1996 Microsoft introduced a new File Allocation Table standard called FAT32 (32-bit), which extends these limits:

     Partition size  FAT32/FAT32X Cluster size 
         0 -   259 MB            512 B [*]
       260 -   511 MB  1 KB =  1024 B [*]
       512 -  8191 MB  4 KB =  4096 B
      8192 - 16383 MB  8 KB =  8192 B
     16384 - 32767 MB 16 KB = 16384 B
     32768 MB -  2 TB 32 KB = 32768 B

    [*] = ONLY if using custom FORMAT drive: /Z:n values!

    Therefore FAT32 wastes a lot less disk space, preserving speedy disk access at the same time.
    More info @ MSKB.

    NOTE: You MUST be using Windows 95B/95C OSR 2.0 - 2.5, 98/98 SE(U) [a.k.a. MS-DOS 7.10], ME [a.k.a. MS-DOS 8.00], 2000, XP, 2003, Vista, 2008 or 7 [no native MS-DOS] to take advantage of FAT32.

    PROs + CONs:

    FAT16/FAT32 versus NTFS/NTFS5 versus FAT64/exFAT comparison.
    Default FAT16, FAT32, NTFS + exFAT cluster sizes when using MS FORMAT tool.
    More info.
    Even more info.

    KNOWN BUGS + FIXES:
    1. Microsoft acknowledged in this MSKB article that Windows 95 retail, 95a OSR1 + 95B/95C OSR 2.x do NOT support disk drives larger than 32 GB. :(
    2. Windows 98 retail, 98 SP1 + 98 SE(U) provide built-in support for media drives > 32 GB, but ONLY IF you install the fixed ESDI_506.PDR [English patch] that allows ScanDskw.exe to properly recognize (E)IDE/(Ultra)ATA hard disk clusters beyond cluster number 967,393.
      More info @ MSKB.
    3. The only Microsoft Operating Systems that natively support drives larger than 32 GB (to date) are Windows NT 4.0, 2000, ME, XP, 2003, Vista, 2008 + 7.
    4. Make sure your motherboard BIOS supports hard disks larger than 137 GB (48-bit LBA function). Always "flash" your BIOS using the current BIOS update from your mainboard vendor's web/ftp site.
      More info @ MSKB.
      Windows 98/98 SE/ME (E)IDE/ATAPI Driver for Hard Disks > 137 GB, also here.

    NEWS FLASH:
    1. Microsoft introduced FAT64 (exFAT) (Extended File Allocation Table) file system for Windows XP/2003/Vista/2008/7 similar to FAT32/FAT32X, but without the limitations that plagued FAT32/FAT32X, designed for SSD + USB Flash drives and compatible with hard drives.
      More info.
      Advantages:
      • largest disk size 512 TB (TeraBytes) (practical limit) or 64 ZB (ZettaBytes) (theoretical limit);
      • largest file size 512 TB (TeraBytes) (practical limit) or 64 ZB (ZettaBytes) (theoretical limit);
      • largest cluster size 32 MB;
      • up to 2,796,202 files per directory;
      • extensible directory structure and file name hashes;
      • improved free space allocation and delete performance due to free space bitmaps;
      • access control lists (ACL) support;
      • Transaction-Safe FAT File System (TFAT) support (WinCE);
      • OEM definable custom file system parameters for specific (portable) devices.
      Disadvantages:
      • backward incompatible with DOS/MS-DOS, Windows 95, 98, ME, NT and 2000;
      • no file system journaling support.
      How to enable FAT64 (exFAT):
    2. Microsoft announced WinFS (Windows Future Storage) secure FAT layer (NOT file system!) for Windows XP/2003/Vista/2008 operating on top of NTFS5 (New Technology File System version 5), capable of holding entire databases instead of just directories/folders.
      More info.

    FAT16, FAT32/FAT32X, NTFS + BIOS limits techno details + specs:

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DISK PARTITIONING, FORMATTING, BACKUP + RECOVERY TOOLS

ALWAYS BACKUP ALL YOUR HARD DRIVES TO A SAFE LOCATION
BEFORE USING ANY TOOLS THAT MODIFY DISK STRUCTURE !

  1. FDISK.EXE is a 16-bit DOS based command line driven tool, the "de facto" Microsoft partitioning utility, located in %winbootdir%\COMMAND (default is C:\WINDOWS\COMMAND) [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00] or in the MS-DOS 6.00/6.20/6.21/6.22 directory (default is C:\DOS or C:\MSDOS).
    Its purpose is to display boot, disk and partition information, modify existing partitions, create new ones and/or delete the ones you want on all installed fixed hard disk(s), but ONLY WITH COMPLETE DATA LOSS! :(
    Starting with Windows 95B OSR 2.0 FDISK has the capability of creating FAT32 partitions of minimum 512 MB on existent drive(s), and of converting your current FAT16 partitions to FAT32, but NOT the other way around WITHOUT COMPLETE DATA LOSS!
    IMPORTANT: To become familiar with the FDISK.EXE command line switches (the documented ones anyway), run one of these commands from any DOS prompt:
    FDISK /?
    or:
    HELP FDISK
    to display the FDISK.EXE help screen.
    Install fixed FDISK.EXE for Windows 98/98 SP1/98 SE(U) to properly detect hard disks larger than 64 GB [English patch].
    More info.
    LIMITATIONS:More FDISK details:

  2. Another Windows 95B/95C OSR 2.x, 98 and ME FAT32 conversion DOS mode 16-bit tool comes also from Microsoft: CVT.EXE [62 KB, free, unsupported].
    More info.
    Newest and most compatible CVT.EXE is found on Windows ME setup CD.
    CVT.EXE preserves disk data integrity. Requires to specify the drive letter to convert. Running CVT without command line parameters displays the help screen.
    Windows 98/ME users can find CVT.EXE in %winbootdir%\COMMAND (usually C:\WINDOWS\COMMAND).
    Run CVT.EXE from a floppy/CD/DVD boot disk or from a hard disk/partition other than the one you want to convert, because if the conversion ends with errors, data on respective disk will be lost.
    The Win98/98 SE version of CVT.EXE may NOT work from native MS-DOS! In this case use the Windows GUI version (Cvt1.exe = see below).
    The little known /CVT32 parameter works ONLY with the Win98/98 SP1/98 SE(U) version of CVT.EXE and allows FAT32 conversion in native MS-DOS mode. Example:
    CVT.EXE D: /CVT32
    This MS TechNet article details all available CVT.EXE parameters.
    More info.
    How to use the WinME version of CVT.EXE.
    [Thank you ERPMan!]
    You canNOT convert a FAT32 partition back to FAT16 using CVT.EXE!
    CVT requires a minimum of 500 KB of free DOS memory. To avoid error messages like:
    "Not enough memory (system) resources"
    while running CVT, disable the loading of some of your DOS mode devices/TSRs, by adding REM in front of the respective lines in your CONFIG.SYS and/or AUTOEXEC.BAT, or use an upper memory manager (like MS EMM386.EXE or UMBPCI.SYS) to load them all "high", in upper memory (UMA). Edit your startup files using EDIT.COM in DOS or Notepad/Sysedit in Windows. Reboot when done.

  3. Windows 98, 98 SE(U) and ME include a graphical FAT32 conversion tool (Cvt1.exe, located in %windir% = default is C:\WINDOWS), capable of converting your existing FAT16 partitions to FAT32 (528 MB minimum size), but NOT the other way around!
    Cvt1.exe actually provides a front end GUI to running the CVT.EXE DOS mode tool (see above), also included with Win98/98 SE(U)/ME (in C:\WINDOWS\COMMAND), but adds extensive help to guide you through the entire process.
    To access the FAT32 conversion tool: click the Start button -> Programs -> Accessories -> System Tools -> FAT32 Converter.

  4. To create FAT32 partitions smaller than 528 MB or to convert FAT16 partitions to FAT32 and BACK:
    • WITH data loss: see the UNDOCUMENTED FDISK parameters below.
    • WITHOUT data loss: get a 3rd party [free(ware)] utility like:

      IMPORTANT: Run ANY DOS based partitioning/formatting tool ONLY from the native/real/true/pure MS-DOS mode OUTSIDE Windows GUI, NOT from a DOS box/session/window INSIDE Windows, even full screen!

    • 3rd party disk partitioning tools that provide support for FAT32X (retail):

      FAT32/FAT32X partitions are NOT compatible with Microsoft DrvSpace/DblSpace compression scheme! The ONLY disk compression tool that recognizes (but does NOT compress) FAT32/FAT32X partitions/disks is included on the Windows 98/ME Setup CD-ROMs!
      So far there is NO disk compression scheme (software) able to compress/double FAT32/FAT32X partitions.

    • Microsoft FAT32 Evaluation Tool [part of Windows 98 Resource Kit (RK)] included on the Windows 98 Setup CD-ROM [97 KB, free] works also with Windows 95B/95C OSR 2.x, 98 SP1, 98 SE(U) and ME. Shows all your drives/partitions specs, sizes and the disk space saved should you decide to convert existing FAT16 partition(s)/disk(s) to FAT32.

    UPDATE: "Thanks for the FAT32 analysis - very comprehensive and understandable. I have only one suggestion:
    You might consider a mention of users with Compressed Hard Drives who cannot use FAT32 and for whom Partition Magic is of little use. Of course, this applies to older machines with their small hard drives, but I read that the average age of PCs in use is about 3 years with many machines well past the 5 year mark. Many of these probably can't or don't run Win9x for various reasons, but for those that do, the substitute to FAT32 is DriveSpace which comes with Microsoft Plus! for Win95 [the Desktop Themes and Pinball game are just space wasting fluff to those with small hard drives]. As a result of using DriveSpace [on a 250 MB hard drive] the cluster size on C: is 8,192 bytes and on H: [the C: Host drive] is 4,096 bytes. The other caveat: minimize cluster waste by deleting unused files, zip several files together if appropriate and send files/programs off to portable drives if possible. If stuck with a small hard drive, apply a "worthy to keep" test to every file that is added."
    [Thank you Ojatex!]

    Below are detailed ALL available FDISK parameters, including the UNDOCUMENTED + HIDDEN ones:

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FDISK.EXE HIDDEN PARAMETERS

  1. FDISK /FPRMT [Windows 95B OSR2 + MS-DOS 7.10 and above ONLY]

    FDISK /FPRMT bypasses the FDISK startup screen, but enables interactive FAT16/FAT32 support. This can be used to force FDISK to create FAT32 partitions smaller than 512 MB, normally not possible by default.
    TIP:
    1. Copy HELP.COM as FDISK.COM .
    2. Open FDISK.COM in a hex editor.
    3. Replace each QBASIC.EXE instance with FDISK.EXE followed by 1 space.
    4. Replace /QHELP with /FPRMT .
    From now on whenever you run FDISK, it won't ask for large/FAT32 disk support anymore.
    To use FDISK without parameters, just run FDISK.EXE.
    [Thank you os2fan2!]

  2. FDISK x /PRI:n (/PRIO:n) /EXT:n /LOG:n (/LOGO:n) [MS-DOS 6.00 and above ONLY]

    FDISK x /PRI:n (or /PRIO:n) /EXT:n /LOG:n (or /LOGO:n) MUST be used together for proper operation. Meaning:
    • x = drive number: 1, 2, 3... etc. Drive 1 corresponds to the 1st hard disk installed (C), drive 2 to second hard disk (D)... etc.
    • /PRI:n = creates a primary partition of size n (in MegaBytes) and makes it bootable (active).
    • /PRIO:n = creates a primary partition of size n (in MegaBytes) and makes it bootable (active) while overriding FAT16/FAT32.
    • /EXT:n = creates an extended partition of size n (in MegaBytes) which holds logical partition(s).
    • /LOG:n = creates a logical drive in the extended partition of size n (in MegaBytes).
    • /LOGO:n = creates a logical drive in the extended partition of size n (in MegaBytes) while overriding FAT16/FAT32.
    If using FAT16 maximum size allowed is 2,047 MB (2 GigaBytes).
    If using FAT32 maximum size allowed is 2,047 GB (2 TeraBytes).
    NOTES:
    • Maximum partition size MUST be equal to or smaller than existing free disk space.
    • /EXT:n and /LOG:n (or /LOGO:n) partition sizes MUST be identical.
    • Only one FDISK "LOG" is allowed per EACH logical drive! Therefore on computers with more than one logical drive you MUST run a separate FDISK x /LOG:n (or /LOGO:n) command for EACH installed drive.
    • ONLY IF using Windows 95B OSR 2.0 + MS-DOS 7.10 or newer: /PRI:n and /LOG:n default to FAT32 on partitions larger than 512 MB, or to FAT16 on partitions smaller than 512 MB. /PRIO:n and /LOGO:n default to FAT16 even on partitions larger than 512 MB, same as older MS-DOS 5.00/6.xx FDISK.
    • ONLY Windows 95B/95C OSR 2.x, 98, 98 SE(U), 2000, ME, XP and 2003 support FAT32.
    • Use /LOGO:n instead of /LOG:n and/or /PRIO:n instead of /PRI:n to ignore FAT information in case of disk access errors.

  3. FDISK /MBR [MS-DOS 6.00 and above ONLY]

    FDISK /MBR recreates the boot sector of the first (bootable) hard disk overwriting it with a fresh copy, by writing a new Master Boot Record (MBR) based on existent disk structure, without altering the partition table information.
    Can be used to repair a damaged/corrupted MBR (i.e. by a virus).

    FYI:

    WARNING: Writing the master boot record to the hard disk in this manner can render certain hard disks partitioned with SpeedStor unusable! It can also cause problems for some dual-boot programs (including Windows 95) or for disks with more than 4 partitions!

    DEFINITION of MBR:
    During the bootup sequence, at the end of the ROM BIOS bootstrap routine, the BIOS will read and execute the first physical sector of the first available floppy or hard drive on the system. This sector is called the Master Boot Record (MBR), or Master Boot Block (MBB), or Partition Table.
    A small program is stored at the beginning of this sector and the partition table is stored at the end of this sector. This program uses the available partition information to determine which partition is bootable (usually the first primary DOS/WIN partition) and attempts to boot from it.

    NOTES:
    • The largest partition MS-DOS beginning with release 5.00 and up to Windows 95a OSR1 versions of FDISK can create/recognize is 2 GB (GigaBytes). The 2 GB partition limit has been overcome by Microsoft (FINALLY!), beginning with Windows 95B OSR 2.0. Named the FAT32 file system, it supports partitions/drives up to 2 TB (TeraBytes).
    • Windows NT4/2000/XP/2003/Vista/2008 have their own 32-bit protected file system called NTFS or NTFS5, INCOMPATIBLE with FAT16 or FAT32!

    WINDOWS 95 AND 95a OSR1 "MBR REFRESH" BUG

    There is a problem when installing a new hard drive on your system under Windows 95 [original retail] or 95a OSR1 [upgraded with SP1].
    If you upgraded from MS-DOS 5.00 (or earlier), your primary hard disk, formatted under your old version of MS-DOS, contains the MBR (the Master Boot Record, also called the boot sector) written by the hard disk formatting utility (FDISK) provided with MS-DOS. When you add another hard disk under Win95, you format and partition it with the Win95/OSR1 (MS-DOS 7.00) version of FDISK.
    This means that each drive was formatted and partitioned under a different OS, but Windows 95/OSR1 WON'T RECOGNIZE YOUR DRIVE! There is nothing wrong, don't panic. :) It's "just" another glitch in the OS, something Microsoft overlooked! :(
    When a drive is formatted/partitioned under Win95/OSR1 the MBR tells the OS that the drive is a Windows (WIN) drive. If your drive was formatted/partitioned under earlier versions of MS-DOS (3.0 - 6.22) the drive is recognized as an MS-DOS (DOS) drive.
    All you have to do is refresh the MBR by running FDISK (the Windows 95/95a OSR1 version) with the UNDOCUMENTED /MBR switch on the old drive, which repairs the boot sector by overwriting it with a fresh copy:
    FDISK /MBR
    The boot record (MBR) will be refreshed without reformatting the drive or losing any data!
    I presumed your primary (old) hard disk has assigned the letter C (single logical partition) and your new (secondary) hard disk is D (also with a single logical partition). Change drive letters if different on your system and/or if you have more than 1 partition per each hard disk.
    This can be done ONLY from native/real/true/pure MS-DOS mode AFTER you EXIT Win95/OSR1 GUI to MS-DOS or (re)BOOT with the "Command prompt only" option from the Startup Menu.
    If the Win95 OS doesn't recognize the new drive, then you can ONLY do this after rebooting into your old MS-DOS version, using the dual-boot feature implemented into Win95 OS. This means you MUST have kept your old MS-DOS files (including FDISK) on your primary (old) hard disk.
    You also need to have kept the old drive as primary (master) and set the new one as secondary (slave).
    Reboot when done. Your (newly installed) hard drive should be recognized by the OS from now on.
    Now you can change the new drive to "master" (primary boot drive) and setup the old one as "slave", especially if the new one is faster.
    Sounds pretty complicated, but you may have to do this some day, and it's better than reformatting the entire drive, and losing precious data.
    There is still another way to refresh/fix the MBR: run the Windows Scandisk tool (Scandskw.exe, located in your main Windows folder) on ALL hard drives on your system. It will automatically refresh the MBR (as needed) if it is damaged.
    See also "USE WINME DEFRAG + SCANDSKW WITH WIN95/98".

    A MUST: Install Microsoft Windows 95/95a OSR1 LBA and INT13 IDE Hard Disk Data Loss DISKTSD.VXD Fix:
    DSKTSUPD.EXE [147 KB, English].

    NOTE: The "MBR BUG" does NOT affect Windows 95B/95C OSR 2.x, 98/98 SE(U) or ME.

    FYI: Partition Magic overcomes the above Windows 95/OSR1 limitation, and makes ANY hard drive compatible with ANY Microsoft operating system and ANY FAT system (and much more). Retails for $30-60 at most computer stores. IMHO it's worth every penny, it saved my "computing life" more than once! :)
    Supports Windows 95B/95C OSR 2.x/98/98 SE(U)/ME FAT32/FAT32X and NT4/2000/XP/2003 NTFS/NTFS5 file system standards.

  4. FDISK /Q [MS-DOS 6.00 and above ONLY]

    FDISK /Q prevents rebooting the computer automatically after altering the partition information by using FDISK with other parameters.

  5. FDISK /STATUS [MS-DOS 5.00 and above ONLY]

    FDISK /STATUS displays a screen similar to using FDISK's option 4: "Partition information", but shows also extended partition information (if any).

  6. FDISK /X [Windows 95 + MS-DOS 7.00 and above ONLY]

    FDISK /X limits disk access to a total of 8.4 GB even on larger physical drives, even if the BIOS supports INT13h extensions for hard disks over 8.4 GB, thus preventing the use of 0E and 0F partition types, by ignoring LBA (Logical Block Addressing) and extended disk information.
    This makes possible disk partitioning on computers with older BIOSes without support for hard disks larger than 8.4 GB.
    Use /X to start FDISK if you receive disk access, stack overflow and/or data corruption error messages.

  7. FDISK /ACTOK [Windows 95B OSR 2.0 + MS-DOS 7.10 and above ONLY]

    FDISK /ACTOK (ACT OK = act as if disk is OK) allows to set an active partition on any hard disk (if present) other than hard disk 0 (default = 128).
    [Thank you JW Rebel!]

  8. FDISK /CMBR x [Windows 95B OSR 2.0 + MS-DOS 7.10 and above ONLY]

    FDISK /CMBR x MUST be used together for proper operation. Recreates the boot sector of the second, third... etc hard disk(s) (if any) overwriting it (them) with a fresh copy, by writing a new Master Boot Record (MBR) based on existent disk structure, without altering the partition table information. Valid values for x:
    • 1 = first (bootable) physical hard disk (same as using FDISK /MBR):
      FDISK /CMBR 1
    • 2 = second (not bootable) physical hard disk (if any):
      FDISK /CMBR 2
    • 3 = third (not bootable) physical hard disk (if any):
      FDISK /CMBR 3
    • ... etc.
    Can be used to repair a damaged/corrupted MBR (i.e. by a virus).

  9. FDISK /PRMT [MS-DOS 6.00 ONLY]

    FDISK /PRMT adds extra prompt ["nagging" :)] screens which require user input (key press) before proceeding further.

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FORMAT.COM HIDDEN PARAMETERS

    FORMAT.COM is an external MS-DOS command, located by default in %winbootdir%\COMMAND (default is C:\WINDOWS\COMMAND) [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00] or in the MS-DOS 6.xx directory (default is C:\DOS or C:\MSDOS) [MS-DOS 6.00 - 6.22].
    IMPORTANT: To become familiar with the FORMAT.COM command line switches (the documented ones anyway), run one of these commands from any DOS prompt:
    FORMAT /?
    or:
    HELP FORMAT
    to display the FORMAT.COM help screen.
    NOTE: FORMAT drive: /Q (documented switch) performs a QUICK format ONLY IF respective drive/partition is already formatted.

  1. FORMAT /AUTOTEST [MS-DOS 5.00 and above ONLY]

    FORMAT /AUTOTEST checks for the existing format of your disk, unless the /U (UNCONDITIONAL) parameter is also used, and then proceeds with an UNATTENDED DISK(ETTE) FORMAT:
    • DOES NOT prompt for a volume label!
    • DOES NOT prompt to format another disk(ette)!
    • NO delay: NO user intervention!
    • Ends WITHOUT pausing!
    After completion, it DOES display disk space statistics, ONLY IF using MS-DOS 5.00/6.xx.
    WARNING: This works on BOTH hard and floppy drives!

  2. FORMAT drive: /BACKUP [MS-DOS 5.00 and above ONLY]

    FORMAT drive: /BACKUP works exactly like /AUTOTEST, applies ONLY to floppy diskettes, but it DOES prompt the user for a volume label, and it DOES display disk space information upon completion.

  3. FORMAT drive: /SELECT [MS-DOS 5.00 and above ONLY]

    FORMAT drive: /SELECT is similar to using the MIRROR command [a MS-DOS 5.00 and earlier ONLY utility, removed from all MS-DOS releases beginning with 6.00], and reads the disk(ette) system area (sector 0).
    In MS-DOS 4.0 FORMAT /SELECT has the same effect as FORMAT /BACKUP.
    [Thank you William!]

  4. FORMAT drive: /U [MS-DOS 5.00 and above ONLY]

    FORMAT drive: /U performs an UNCONDITIONAL format, which DESTROYS every byte of data on ANY hard disk/floppy by overwriting it with zeroes (hex F6h).
    WARNING: ANY disk(ette) formatted using /U canNOT be UNFORMATTED!

  5. FORMAT drive: /SELECT /U [MS-DOS 5.00 and above ONLY]

    FORMAT drive: /SELECT /U makes a disk(ette) UNREADABLE by filling the system area (sector 0) with zeroes (hex F6h), due to using these two incompatible options together. All other sectors are left intact.
    [Thank you William!]
    WARNING: NEVER use these two FORMAT switches TOGETHER on ANY drive!

  6. FORMAT drive: /Z:n [Windows 95B OSR 2.0 + MS-DOS 7.10 and above ONLY]

    FORMAT drive: /Z:n formats a FAT32 drive with a cluster size of n times (multiple of) 512 Bytes.
    Meaning:
    drive: = your hard drive letter: C:, D:, E:... etc.
    n = number of sectors per cluster multiplied by 512 (cluster size in Bytes).
    n = 1, 2, 4, 8, 16, 32 or 64 .
    Examples:
    n = 1 creates a 512 Bytes cluster;
    n = 2 creates a 1024 Bytes (1 KB) cluster;
    n = ? creates a ? x 512 = ???? Bytes (???? Bytes : 1024 = ? KB) cluster.
    You can modify the size of the allocation units (sectors) on a FAT32 drive to your heart desire.
    The /Z:n parameter canNOT be used with floppy/removable drives.
    WARNING: It is NOT recommended to change default cluster size because certain programs such as disk-repair/anti-virus tools may STOP working properly!

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HIMEM.SYS HIDDEN PARAMETERS

    HIMEM.SYS is the Microsoft high/upper/extended memory manager, located by default in C:\WINDOWS [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00], C:\DOS or C:\MSDOS [MS-DOS 5.00/6.xx].
    Windows (ANY release) canNOT start without HIMEM.SYS loaded!
    HIMEM.SYS can be loaded ONLY in CONFIG.SYS using the DEVICE command. Example:
    DEVICE=drive:\path\HIMEM.SYS /TESTMEM:OFF /Q
    HIMEM.SYS's DEVICE line MUST appear in CONFIG.SYS before ANY other device drivers loaded with DEVICE, DEVICEHIGH, INSTALL or INSTALLHIGH, including EMM386.EXE.
    HIMEM.SYS provides access to the High Memory Area (HMA), Upper Memory Area (UMA) and coordinates the use of the computer's extended memory, so that no two programs or device drivers use the same memory area at the same time.
    IMPORTANT: To become familiar with the HIMEM.SYS command line switches (the documented ones anyway):

    DEVICE=drive:\path\HIMEM.SYS /Q [MS-DOS 6.00 and above ONLY]

    HIMEM.SYS /Q (QUIET) disables the display of HIMEM.SYS loading status during bootup. Only error messages will be shown, IF the Logo=0 line exists in MSDOS.SYS, under the [Options] section, valid ONLY for Windows 95/98/ME OS.
    This switch is valid ONLY for HIMEM.SYS versions 3.10 [MS-DOS 6.00 - 6.22] up to 3.95 [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00].
    Example:
    DEVICE=C:\WINDOWS\HIMEM.SYS /Q

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MEM.EXE HIDDEN PARAMETERS

    MEM.EXE is an external MS-DOS command, located by default in %winbootdir%\COMMAND (default is C:\WINDOWS\COMMAND) [Windows 95/98/ME, a.k.a. MS-DOS 7.00/7.10/8.00] or in the MS-DOS 6.xx directory (default is C:\DOS or C:\MSDOS) [MS-DOS 6.00 - 6.22].
    IMPORTANT: To become familiar with the MEM.EXE command line switches (the documented ones anyway), run one of these commands from any DOS prompt:
    MEM /?
    or:
    HELP MEM
    to display the MEM.EXE help screen.

    MEM /A [MS-DOS 6.00 and above ONLY]

    MEM /A (ALL) displays a short summary screen of your memory configuration and also the status of the HMA.
    HMA (High Memory Area) is a little known 64 KB area just above the first MegaByte (1 MB = 1,024 KB = 1,048,576 Bytes) of RAM as mapped by Microsoft HIMEM.SYS memory manager or another 3rd party upper/extended/expanded memory manager, like Quarterdeck QEMM386, Helix NetRoom RM386, Qualitas 386MAX, Lineo DR-DOS EMM386 etc.
    Part of the DOS resident module and DOS BUFFERS usually load into the HMA, ONLY IF this memory region is free at bootup.
    Example of MEM /A output display (only the HMA info shown here):

    "Available space in High Memory Area     1K     (944 bytes)
 MS-DOS is resident in the high memory area."

    To display ALL available memory configuration at a DOS prompt, run:
    MEM /A /C /P
    or if you prefer technical details (conventional/upper memory regions map and exact hex addresses where all loaded devices/drivers/TSRs reside), run:
    MEM /D /P
    NOTE: High DOS is enabled by this CONFIG.SYS line (the "HIGH" switch):
    DOS=HIGH,UMB

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VER HIDDEN PARAMETERS

    VER is an internal MS-DOS command, built into COMMAND.COM. An actual file does not exist.
    IMPORTANT: To become familiar with the VER command line switch (the documented one anyway), run one of these commands from any DOS prompt:
    VER /?
    or:
    HELP VER
    valid for all MS-DOS 6.xx and Windows 95/98/ME users.

    VER /R [MS-DOS 5.00 and above ONLY]

    VER /R (REVISION) displays extended DOS info: the DOS revision and the memory location of the DOS module, in addition to using the plain VER command.
    Example of screen output for plain VER command (using Win98 SE + MS-DOS 7.10):

    "Windows 98 [Version 4.10.2222]"

    Example of screen output for VER /R command (using Win98 SE + MS-DOS 7.10):

    "Windows 98 [Version 4.10.2222]
     Revision A
     DOS is in HMA    "

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WIN.COM HIDDEN PARAMETERS

    WIN.COM is the Windows GUI (Graphical User Interface) command line executable located in %winbootdir% (default is C:\WINDOWS).
    IMPORTANT: To become familiar with the WIN.COM command line parameters (the documented ones anyway):FYI: Microsoft removed ALL undocumented WIN.COM switches detailed below from Windows Millennium Edition (ME)!

  1. WIN /MQ [Windows 95B OSR 2.1 and above ONLY]

    WIN /MQ automatically restarts the computer (soft reboot), without prompting or waiting for input (key press). This is similar to Quarterdeck QEMM's QuickBoot, which calls INT19h to reboot almost instantaneously (VERY FAST!) without performing any BIOS/CMOS hardware or OS/software checking.
    CAUTION: This fast reboot routine may generate error messages and/or lockups!
    This switch works ONLY IF executed from the native/real/true/pure MS-DOS mode OUTSIDE the Windows 95/98 GUI, NOT from WITHIN Windows in a DOS box/session.
    This DOS secret suggested by phish.

  2. WIN /W [Windows 95 and above ONLY]

    WIN /W generates this message:

    "Press any key to continue...
     Pressing a key reboots back to Windows 95 (98).    "

    waiting for user input (key press), and then restarts the computer (warm reboot), restoring the original CONFIG.SYS and AUTOEXEC.BAT files in the root directory of the boot drive from CONFIG.WOS and AUTOEXEC.WOS (if any). This is useful when the computer is restarted after interrupting a "single" mode MS-DOS session, because of this CONFIG.SYS line:
    DOS=SINGLE
    which does NOT allow Windows 95/98 GUI to load.
    This switch works ONLY IF executed from the native/real/true/pure MS-DOS mode OUTSIDE the Windows 95/98 GUI, NOT from WITHIN Windows in a DOS box/session.
    NOTES:
    • The .WOS files are created when you run a DOS based program that requires a separate MS-DOS reboot setup (in "single" mode), and you have selected the "Specify a new MS-DOS configuration" check box in the PIF file Properties tab.
    • For more details see "MS-DOS PROMPT", also in MYTIPS95.TXT (part of W95-11D.EXE).

  3. WIN /WX [Windows 95 and above ONLY]

    WIN /WX automatically restarts the computer (warm reboot), without prompting or waiting for input (key press), and restores the original CONFIG.SYS and AUTOEXEC.BAT files in the root directory of the boot drive from CONFIG.WOS and AUTOEXEC.WOS (if any). This is useful when the computer is restarted after interrupting a "single" mode MS-DOS session, because of this CONFIG.SYS line:
    DOS=SINGLE
    which does NOT allow Windows 95/98 GUI to load.
    This switch works ONLY IF executed from the native/real/true/pure MS-DOS mode OUTSIDE the Windows 95/98 GUI, NOT from WITHIN Windows in a DOS box/session.
    NOTES:
    • The .WOS files are created when you run a DOS based program that requires a separate MS-DOS reboot setup (in "single" mode), and you have selected the "Specify a new MS-DOS configuration" check box in the PIF file Properties tab.
    • For more details see "MS-DOS PROMPT", also in MYTIPS95.TXT (part of W95-11D.EXE).

  4. WIN /Z [Windows 95B OSR 2.1 and above ONLY]

    WIN /Z automatically forces the ATX power supply to (soft-)power off the computer ONLY on ATX motherboards, without prompting or waiting for input (key press).
    This switch works ONLY IF executed from the native/real/true/pure MS-DOS mode OUTSIDE the Windows GUI, NOT from WITHIN Windows in a DOS prompt/box/session.
    This DOS secret suggested by Shaminda.

  5. WIN : [Windows 3.xx + WfWG 3.1x ONLY]

    WIN : starts Windows 3.xx or Windows for WorkGroups 3.1x WITHOUT displaying the startup logo (RLE encoded, 16 colors).
    This switch works ONLY IF executed from the native/real/true/pure MS-DOS mode OUTSIDE the Windows/WfWG GUI, NOT from WITHIN Windows/WfWG in a DOS prompt/box/session.
    CAUTION: This switch may cause sudden lockups with some older video controllers!
    NOTE: To learn about another (SAFE) method of starting Windows/WfWG 3.1x without a logo, see NEWLOGO.TXT (part of W31-11D.ZIP).

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©1996-2010 MDGx (AXCEL216): Everything here is FREEware. I have created [August 1996], maintain and update these web pages entirely by hand using Programmer's File Editor [replaced Notepad]. I do not promote, speak in the behalf of, advertise or work for any computing, news or internet profit business. All ®registered ©copyrights and ™trademarks referred herein retain the property of their respective owners.

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