What youb told us, sounds like your computer is infected for some kind of virus that maybe is in your mbr or something like that, my first shot will be if you can find a good antivirus with the lastest update and scan your puter that will solve your problem if that doesn't work i'll better loose my files or bakup it first and start with a clean install of win98se
the format c:/q it's for a quick format i won't suggest that but i'll work but i'll suggest a format c:/u/c just in case
hope that will help you