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Contents of the Windows Msdos.sys File

This article was previously published under Q118579
SUMMARY
The Windows Setup program creates a file called Msdos.sys in the root folder and sets the file with the Read-Only, System, and Hidden attributes. Unlike the Msdos.sys file in MS-DOS, this file is a text file. It contains a [Paths] section that lists the locations for other Windows files (such as the registry) and an [Options] section that you can use to personalize the boot process.
MORE INFORMATION
The [Paths] section can contain the following settings:
  • HostWinBootDrv=Root of Boot Drive
    Default: C
    Purpose: Specifies the location for the root of the boot drive.
  • UninstallDir=Root of Boot Drive
    Default: C
    Purpose: Specifies the location of the W95undo.dat and W95undo.ini files. These files are necessary to uninstall Windows 95.

    NOTE: This setting is present only if you back up your system files when you are prompted during Windows 95 Setup.
  • WinBootDir=Windows Folder
    Default: Folder specified during Setup (for example, C:\Windows)
    Purpose: Lists the location of the necessary files for booting.
  • WinDir=Windows Folder
    Default: Folder specified during Setup (for example, C:\Windows)
    Purpose: Lists the location of the Windows 95 folder specifiedduring Setup.
The [Options] section can contain the following settings. You must manually insert these settings if you want to use them:
  • AutoScan=Number
    Default: 1
    Purpose: Defines whether or not ScanDisk is run after a bad shutdown.A setting of 0 does not run ScanDisk; 1 prompts beforerunning ScanDisk; 2 does not prompt before runningScanDisk but prompts you before fixing errors if anyerrors are found.

    This setting is used only by OEM Service Release 2 and Windows 98.
  • BootDelay=SecondsDefault: 2Purpose: Sets the amount of time the "Starting Windows" messageremains on the screen before Windows 95 continues to boot.

    NOTE: BootDelay is not supported in Windows 98.
  • BootSafe=Boolean
    Default: 0
    Purpose: A setting of 1 forces your computer to boot in Safe mode.
  • BootGUI=Boolean
    Default: 1
    Purpose: A setting of 1 forces the loading of the GUI interface. Asetting of 0 disables the loading of the GUI interface.
  • BootKeys=Boolean
    Default: 1
    Purpose: A setting of 1 enables the use of the function key bootoptions (that is, F4, F5, F6, F8, and CTRL). A setting of 0disables the use of these function keys during the boot process

    NOTE: A setting of BootKeys=0 overrides the use of BootDelay=n.
  • BootMenu=Boolean
    Default: 0
    Purpose: A setting of 1 enables the Startup menu. If this setting is 0,then you must press the F8 key when "Starting Windows 95"appears, (or press and hold the CTRL key when your Windows98-based computer restarts) to invoke the Startup menu.
  • BootMenuDefault=Number
    Default: 1 if the system is running correctly; 3 if the system hung in the previous instance
    Purpose: Use this setting to set the default menu item for startup.
  • BootMenuDelay=Number
    Default: 30
    Purpose: This setting is used to set the number of seconds your systemwill pause on the Startup menu. If the number of seconds countsdown to 0 without intervention, the BootMenuDefault is activated.

    NOTE: This option is not functional unless BootMenu=1 has been added to the [Options] section of the Msdos.sys file.
  • BootMulti=Boolean
    Default: 1
    Purpose: A setting of 0 disables the multi-boot option. (For example,with a setting of 0 you cannot boot your previous operatingsystem.) A setting of 1 enables the F4 and F8 keys to boot yourprevious operating system.
  • BootWarn=Boolean
    Default: 1
    Purpose: A setting of 0 disables the Safe-mode boot warning message andthe Startup menu.
  • BootWin=Boolean
    Default: 1
    Purpose: A setting of 1 forces Windows 95 to load at startup. A settingof 0 disables Windows 95 as your default operating system (thisis useful only if you have MS-DOS version 5.x or 6.x on thecomputer).

    NOTE: Pressing F4 inverts the default only if BootMulti=1. (For example, pressing the F4 key with a setting of 0 forces Windows 95 to load.)
  • DoubleBuffer=Boolean
    Default: 0
    Purpose: A setting of 1 is a conditional setting that enables double-buffering for controllers that need it (for example, SCSIcontrollers). A setting of 2 is an unconditional setting thatenables double-buffering regardless of whether the controllerneeds it or not.
  • DBLSpace=Boolean
    Default: 1
    Purpose: A setting of 1 allows the automatic loading of the DBLSPACE.BINfile. A setting of 0 prevents the automatic loading of thisfile.

    NOTE: Windows 95 uses either Dblspace.bin or Drvspace.bin if either is present in the root folder of the boot drive at startup. To disable acompression driver from being loaded at startup, use both settings in theMsdos.sys file. For example:
    DBLSpace=0
    DRVSpace=0
  • DRVSpace=Boolean
    Default: 1
    Purpose: A setting of 1 allows the automatic loading of the DRVSPACE.BINfile. A setting of 0 prevents the automatic loading of this file.

    NOTE: Windows 95 uses either Dblspace.bin or Drvspace.bin if either is present in the root folder of the boot drive at startup. To disable acompression driver from being loaded at startup, use both settings in theMsdos.sys file. For example:
    DBLSpace=0
    DRVSpace=0
  • LoadTop=Boolean
    Default: 1
    Purpose: A setting of 0 does not let Windows 95 load COMMAND.COM orDRVSPACE.BIN/DBLSPACE.BIN at the top of 640K. If you are havingcompatibility problems with software that makes assumptions aboutthe available memory try setting this to 0.
  • Logo=Boolean
    Default: 1
    Purpose: A setting of 1 forces the default Windows 95 logo to appear. Asetting of 0 prevents the animated logo from being displayed.A setting of 0 also avoids hooking a variety of interruptsthat can create incompatibilities with certain third-partymemory managers.
  • Network=Boolean
    Default: 0
    Purpose: A setting of 1 means the network was installed and adds Safe mode with network support as an option on the Windows 95 Startup menu.

Extra Characters in the Msdos.sys File

The Msdos.sys file also contains a section that contains seemingly uselessinformation. This information is necessary to support programs that expectthe Msdos.sys file to be at least 1,024 bytes in length. For example, if anantivirus program detects that the Msdos.sys file is less than 1,024bytes, it may assume that the Msdos.sys file is infected with a virus. Ifyou delete the Msdos.sys file your computer will not start.

The following statement, followed by a series of "X"s, appears in theMsdos.sys file:
;The following lines are required for compatibility with other programs.
;Do not remove them (Msdos.sys needs to be > 1024 bytes).
Because each line begins with a semicolon (;), the lines are not read by Windows.

How to Edit the Msdos.sys File

If you want to change any of the values in the Msdos.sys file, followthese steps to edit the file:
  1. Click Start, point to Find, and then click Files Or Folders.
  2. In the Named box, type msdos.sys. In the Look In box, click your boot drive (usually drive C, or drive H if drive C is compressed). Click the Find Now button.
  3. Right-click the Msdos.sys file, and then click Properties.
  4. Click to clear the Read-Only and Hidden check boxes to remove these attributes from the Msdos.sys file, and then click OK.
  5. Right-click the Msdos.sys file, and then click Open With.
  6. In the Choose the program you want to use box, click WordPad, and then click OK.
  7. Make the changes you want to the Msdos.sys file. When you are done,save the file as a text document, and then quit WordPad.
  8. Right-click the Msdos.sys file, and then click Properties.
  9. Select the Read-Only and Hidden check boxes to set the attributes for the file, and then click OK. Close the Find window.
  10. Restart Windows.
For additional information about how to determine in which folder Windows is installed, click the article number below to view the article in the Microsoft Knowledge Base:
305792 How to Determine Which Folder Windows Is Installed In
msdos sys
Properties

Article ID: 118579 - Last Review: 01/19/2007 04:52:43 - Revision: 1.4

  • Microsoft Windows 95
  • Microsoft Windows 98 Standard Edition
  • Microsoft Windows 98 Second Edition
  • Microsoft Windows Millennium Edition
  • Microsoft Windows 98 Standard Edition
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