MSDOS.SYS

Take control of your Windows 95/98/ME machine at DOS level!

After all Windows 95/98/ME is a MIXED (read “partially enabled”) 32-bit AND 16-bit [for backward compatibility with MS-DOS (DOS16 and DOS32) and older 16-bit Windows/WfWG 3.xx (Win16) programs] Graphical User Interface (GUI) protected mode virtual environment (… sorry, Operating System), which still depends on the good old MS-DOS 7.xx TSR modules (IO.SYS + COMMAND.COM), MS-DOS mode memory manager (HIMEM.SYS) and compatibility (legacy) drivers (IFSHLP.SYS) to load on top of the plain DOS command line based layer!

The good news is Microsoft released Windows XP (eXPerience)/2003/Vista/2008/7/8/8.1/2012/10/2016/2019/11/2022, true 32-bit/64-bit multitasking, multithreading and Symmetrical MultiProcessing (SMP) graphical OSes, which aim to do away once for all with the “ancient” 16-bit MS-DOS command line.

All these MSDOS.SYS tips + guidelines (and much more) are also available as part of Windows 95/98/NT4/2000/ME/XP/2003 + DOS 7.xx/8.00 ©Tricks + Secrets Files (W95-11D.EXE), FREEware.

If you'd like to see how my MSDOS.SYS file looks like, and to view my DOS conventional + upper memory optimized CONFIG.SYS + AUTOEXEC.BAT startup files, head on to my MS-DOS 7.xx MEMory Specs Page.

MSDOS.SYS [MicroSoft DOS SYStem] is a vital (the OS is unable to load without it or without WINBOOT.INI, its replacement) Windows 95/98/ME text/ASCII system file, loads Windows 9x/ME OS boot options and paths settings upon bootup, is located in the root directory/folder of the boot drive/partition (default is C:\), has by default (but not necessary for proper operation) Hidden (H), Read-only (R) + System (S) file attributes, and can be edited with Notepad in Windows or EDIT.COM in DOS.

During the OS bootup sequence MSDOS.SYS is processed after IO.SYS.

MSDOS.SYS (or at least WINBOOT.INI) must exist in the root directory/folder of the boot drive/partition [usually C:\ = replace with your actual Windows 9x/ME drive/partition letter if different on your computer], and must contain at least these lines [WINDOWS = replace with your actual Windows 9x/ME main directory/folder name if different on your computer] for proper OS bootup:

[Paths]
WinDir=C:\WINDOWS
WinBootDir=C:\WINDOWS
HostWinBootDrv=C

If MSDOS.SYS (and WINBOOT.INI) is (are) absent, the OS bootup sequence will stop at the native/real/true/pure MS-DOS mode C:\ prompt, and will display an error message.

You can edit/view/print MSDOS.SYS using Notepad.exe in Windows (Windows default ASCII/text editor = usually C:\WINDOWS\NOTEPAD.EXE) or EDIT.COM in DOS [MS-DOS default ASCII/text editor = usually C:\DOS\EDIT.COM (MS-DOS 6.xx) or C:\MSDOS\EDIT.COM (MS-DOS 6.xx) or C:\WINDOWS\COMMAND\EDIT.COM (Win95/98/ME)].

Before editing you MUST strip MSDOS.SYS of its default attributes [Hidden (H), Read-only (R) and System (S)], to be able to modify it.

C:\>attrib -h -r -s msdos.sys

After making your desired modifications to MSDOS.SYS, save it, exit the text editor, and then reboot your machine so the changes can take effect.

Optional: restore MSDOS.SYS attributes back to the original: Hidden, Read-only, System.

C:\>attrib +h +r +s msdos.sys

NOTE: Alternatively you can use one of these freeware MSDOS.SYS Editors to tweak ALL MSDOS.SYS parameters (including the UNDOCUMENTED ones) from a single, easy to use interface.

WINBOOT.INI MUST contain the SAME EXACT lines as MSDOS.SYS so Windows can boot properly. In such case MSDOS.SYS can be moved/deleted altogether, but BEWARE of certain programs that may rely on its presence for proper operation.

Therefore if doing this manually, you need to edit MSDOS.SYS first, make your desired changes, and only after that you need to copy it as WINBOOT.INI (overwriting the original one), to make sure BOTH their contents remain IDENTICAL.

WINBOOT.INI is NOT renamed by Win9x/ME if dual-booting to an older MS-DOS version, so it can be also edited from MS-DOS 6.xx, in which case it is copied as MSDOS.W40 (which is actually MSDOS.SYS renamed by the Win9x/ME dual-boot routine).

Some (still) prefer to dual-boot: keep the ol' MS-DOS version 6.xx (+ Windows/WfWG 3.1x) and have Win9x/ME installed in a separate directory. This way you have the choice to boot with your Win9x/ME configuration, or with your old version of MS-DOS, and eventually use Windows/WfWG 3.1x (only if you kept them!).

If you dual-boot [see “DUAL BOOT” in MYTIPS95.TXT (part of W95-11D.EXE) for details] and choose to boot with your ol' MS-DOS version 6.xx, MSDOS.SYS is renamed to MSDOS.W40.

If also using MS-DOS 6.xx, make sure the DOS directory (default C:\MSDOS or C:\DOS) is mentioned in your path, on the PATH line in your AUTOEXEC.BAT or CONFIG.SYS, and that EDIT.COM resides in your DOS directory or in a directory in your path.

From now on, you'll be able to view/edit MSDOS.SYS contents using your favorite text editor (all Windows 9x/ME releases install both MS-DOS EDIT.COM and Windows Notepad). Change/add MSDOS.SYS entries to customize your system, then save your changes and close the editor when you're done.

You MUST reboot your machine for the new settings to take effect, ONLY IF you have modified MSDOS.SYS.

ALL MSDOS.SYS parameters, even those UNDOCUMENTED, what they do, and how to tweak them to MAXIMIZE your Windows 95/98/ME machine performance, are listed in this table.

MSDOS.SYS consists of 2 sections and supports all following entries: