Msdos.sys is a hidden, system, read-only text file located in the root of the computer's boot drive. This text file contains paths to important files and directories and supports an options section called [Options], which can be used to customise the start-up process.

The following example shows a typical file with default values:



Most values in the [Options] section are Boolean that is, the value can be 1 (enabled) or 0 (disabled).

[Paths] section


Defines the location of the boot drive root directory. Defines the location of the necessary start-up files.


The default is the directory specified during Setup, for example, C:\Windows.


Defines the location of the Windows 98Windows 98 directory as specified during Setup.

[Options] section


Enables scandisk to run automatically when your computer restarts. The default is 1. When this value is set to 1, ScanDisk will run automatically, you will be prompted if you want to run ScanDisk; if you do not respond after one minute, ScanDisk runs automatically. Setting this value to 0 disables this feature. Setting it to 2 launches ScanDisk automatically (if needed), without prompting you.


Sets the initial start-up delay to n seconds. The default is 2. BootKeys=0 disables the delay. The only purpose of the delay is to give the user sufficient time to press F8 after the Starting Windows message appears.


Enables Safe Mode for system start-up. The default is 0. (For Installation equipment manufacturers typically enable this setting).


Enables automatic graphical start-up into Windows 98. This is equivalent to putting the win statement in Autoexec.bat. The default is 1.


Enables the start-up option keys (that is, F5, F6, and F8). The default is 1. Setting this value to 0 overrides the value of BootDelay=n and prevents any start-up keys from functioning. This setting allows system administrators to configure more secure systems.


Enables automatic display of the Windows 98 Start-up menu when set to 1. The default is 0.


Sets the default menu item on the Windows Start-up menu; the default is 3 for a computer with no networking components and 4 for a networked computer.


Sets the number of seconds to display the Windows Start-up menu before running the default menu item. The default is 30.


Enables dual-boot capabilities. The default is 0. MS-DOS can be started by pressing F4 at the Starting Windows message or from the start-up menu when this value is set to 1.


Enables the Safe Mode start-up warning. The default is 1.


Enables Windows 98 as the default operating system. Windows 98 is no longer the default when this value is set to 0; this is useful only with MS-DOS version 5 or 6.x on the computer. The default is 1.


Enables automatic loading of Dblspace.bin. The default is 1.


The default is 0. Setting this value to 1 enables double buffering, if required by the SCSI controller.


Enables automatic loading of Drvspace.bin. The default is 1.


Enables loading of or Drvspace.bin at the top of 640K memory. The default is 1. Set this value to 0 with Novell NetWare or any software that makes assumptions about what is used in specific memory areas.


Enables display of the animated logo. The default is 1. Setting this value to 0 also avoids hooking a variety of interrupts that can create incompatibilities with certain memory managers from other vendors.


Safe Mode With Networking is no longer supported in Windows 98. This value should be set to 0 or left blank to disable this feature.