Get Familiar With MSDOS.SYS

By: Stephen Bucaro

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Get Familiar With MSDOS.SYS

By Stephen Bucaro

Msdos.sys was one of the three files (along with io.sys
and that DOS 6 and earlier versions was
composed of. It was a binary file that created a disk
buffer and file control block for service routines, and
performed hardware initialization. Beginning with
Windows 95, msdos.sys was combined into io.sys and the new
msdos.sys became a text editable configuration file.

Msdos.sys is a hidden system file located in the root of
your boot drive. To view hidden files, in Explorer's
"View" menu select "Folder Options". In the "Folder
Options" dialog box click on the "View" tab and under
"Hidden Files" check "Show all files". You may want to
make a backup copy of msdos.sys named msdos.sys.bak before
you make any changes to the file.

There are three sections to msdos.sys. The [Paths] section
tells Windows where to find the necessary startup files.
The WinDir= entry contains the path to the folder
containing the operating system. The WinBootDir= entry
contains the path to the boot folder. The WinBootDrv=
entry contains the letter of the boot drive. You shouldn't
make any changes to this section.

The [Options] section is used to configure startup
settings. The last section of the file is filler to make
sure the file is at least 1,024 characters long. Before
you can edit the msdos.sys file you need to right-click on
the file name and in the "Properties" dialog box that
appears, uncheck the Read-only attributes check box.

The [Options] section can contain up to 16 entries.

default msdos.sys usually contains only five entries. You
can edit these settings in Notepad for purposes of
debugging or just to make it start faster. Below is a list
of some useful entries.

AutoScan - Controls whether Windows runs ScanDisk after an
improper shutdown. If you have a large hard disk, ScanDisk
can take a long time. You may want to prevent it from
running automatically. Setting AutoScan=0 prevents
ScanDisk from running automatically.

BootGUI - Controls whether your system starts in Windows
mode or DOS 7 mode. Setting BootGUI=0 causes it to start
in DOS mode. (Note: Windows Me does not support booting in
DOS mode, so this will have no effect.)

BootKeys - Controls whether Windows will recognize keys
pressed during startup. You might want to press F8 or Ctrl
during startup to display the Startup Menu. However, if
you want to keep unauthorized people from bypassing your
logon, you should set BootKeys=0 to ignore keys presses
during startup.

BootMenu - If you want the Startup Menu to appear each
time that you start Windows, set BootMenu=1.

BootMenuDefault - Specifies the Startup Menu command that
is highlighted and selected by default when the Startup
Menu appears. Set this to one of the menu numbers shown

3=Safe Mode
5=Command prompt only
6=Safe Mode command prompt only

BootMenuDelay - Sets the delay in seconds that the Startup
Menu is displayed before the default option is
automatically executed.

BootMulti - If you had DOS on your computer when Windows
was installed, BootMulti=1 puts the option to boot from
this previous version of DOS in the Startup Menu.
(Windows Me does not support booting in DOS mode.)

BootSafe - For the thousands of Windows users whose system
stopped working properly years ago, set BootSafe=1 to
start in Safe Mode automatically.

BootWarn - Again, for the thousands of Windows users whose
system stopped working properly years ago. Set BootWarn=0
to start normally even if the previous boot failed. But
because you haven't fixed what's preventing Windows from
starting properly in the first place, this may cause your
system to freeze up with the "blue screen of death".

BootWin - If you had DOS on your computer when Windows was
installed, setting BootWin=0 causes your system to boot to
previous version of DOS rather than Windows. (Not
Windows Me).

Logo - Setting Logo=0 will prevent the Windows logo from
being displayed during startup. This is useful if you
want to see system messages rather than Microsoft's logo
during startup.

There are several other msdos.sys [Option] settings that
are of limited usefulness. AlsoBusiness Management Articles, don't be surprised if any
of these options don't work the way Microsoft claims they
do in the Windows Resource Kit. But you can try using
these settings to change the way Window starts for
purposes of debugging or to make it start faster.
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