Under Win98, I had checked under the computer properties and it displayed that the computer is running under MS-dos compatibility mode.I checked Details, and it mentioned that the computer won't be able to run at optimum performance. I don't know how to find out what's causing this and how to fix it.The MS-DOS prompt in the start menu also won't work unless the com restarts. It doesn't normally do this. Help me plz!

My first guess would be a master boot record virus like NYB. go to WWW.SYMANTEC.COM and download the trial version of norton antivirus that pertains to your system. better yet, if one of your friends owns norton systemworks, or you purchase it yourself, the 3 disk rescue set that comes packaged in the box with the program will be able to remove most MBR viruses. other hunches of mine are a driver like stacker or 3'rd party caching program loading in config.sys, a line in system.ini that says 32bitdiskaccess=false, improperly configured or disabled bus master IDE controllers (www.bmide.com)

The most likely reason is that you have loaded a real mode driver. If you have a CDROM driver or such in your Config.sys or autoexec.bat, remove them. Win9x doesn't use them and it pisses off the OS.

to clear virus in the master boot record run fdisk /mbr in dos mode most likely its in the config.sys or autoexec.bat file that puts in dos mode

The problem is most likely an incompatible CD Rom driver. You must go into your system registry and take out any entry that says "NoIDE" - You can find it by running the "find" function in the system registry. If it does it again, try reloading your CDRom drivers.

I recently ran into this problem and after trying every fix I could find on the net, including all of the fixes listed here. I then tried installing an older drive I had and reinstalling windows98. I started getting HardDrive not found errors. This made me wonder about my ide ribbon cable. I was using an ultradma 66 ribbon cable and more often than not, my system would boot up but MS-DOS compatibilty mode would be present. After I changed the ribbon cable, my system came up normal again.