LeeShanok Technical Support

Customize MSDOS.SYS

By Kate Botello

You may already know that the MSDOS.SYS specifies your boot directory, but did you know that you can customize it?

First, let's take a look at your MSDOS.SYS file. It's located in your root directory. You'll have to unhide it and turn off the read-only attribute first. To do that, right-click on it, go to Properties, then uncheck the appropriate boxes. Now that you're in, the file should look something like the example below.

The place where we can really have some fun is in the Options section. Don't mess with the "random" looking stuff at the end of the file. MSDOS.SYS has to be exactly 1,024 bytes long for compatibility with other programs.

Microsoft's site warns that if your MSDOS.SYS file is any size other than 1,024 bytes, your antivirus software will assume it's been infected with a virus. So it's best (in fact, essential) to leave that part be, and focus on the Options section, where you can actually do some cool stuff.

I'm going to list a few here. For the rest, check out Microsoft's Knowledge Base article.

Turn AutoScan on or off. his defines whether or not ScanDisk runs automatically after your machine crashes. It's best to go ahead and leave this one on. You never know when a crash has corrupted a file, and the whole process only adds about a minute to your boot-up process. Nonetheless, here's the setting:

AutoScan=1

The default is ON. You'll get a prompt before ScanDisk runs. To turn it off, use:

AutoScan=0

If you try:

AutoScan=2

ScanDisk will run automatically, without a prompt, but will prompt you to fix errors if it finds them.

Boot directly into safe mode. Forces your machine to boot directly into safe mode. This might be helpful if your function keys aren't working, and you're having hardware problems.
BootSafe= 1
The default is OFF:
BootSafe=0
Boot the GUI-- or don't.
For those of you who want to dig around at a DOS prompt before you get into the whole Windows thing.
BootGUI=1
Default is ON. This boots the Windows 98 GUI automatically. To get to a command prompt instead, try:
BootGUI=0
This doesn't always work. I played with this on my machine. Basically the end result is that to run Windows you'll have to type WIN at the C:\ prompt.
Show the boot menu-- or don't.
In Windows 95, holding down the F8 key will bring up the boot menu, allowing you to choose different modes (Normal, Safe Mode, Command Prompt Only, etc.). In Windows 98, holding down the Control key on startup will bring up the menu. If you want it to come up every time, without having to hold down a key, use:
BootMenu=1
The default is OFF. The ON setting enables the startup menu, without having to hold down F8 or Control.
And the big one that got us started on the whole MSDOS.SYS shebang, answering a question for Leo. "Where do you set the length of time the boot menu stays up?" Here you go, Leo:
BootMenuDelay=
After the = sign, put in the number of seconds you'd like the boot menu to stay up. The default is 30 seconds. After the seconds time out, your BootMenuDefault (default menu for startup) will load automatically. Now, of course, this doesn't work unless you have BootMenu=1 in the Options section.

And there you have it-- fun with MSDOS.SYS! Now, we've done all this the manual way. Many of these settings (including the answer to Leo's question) are accessible in TweakUI. Do check out Microsoft's Knowledge Base article about this file. There are quite a few more switches you can play with.

Enjoy, supergeeks! -- Kate Botello

File Example

Questions? Answers?