I once had a virus where my drive would think, then the computer's drive next to me would think(I have a network...)  But it is pretty common for computers to do this, at least I've seen it alot with 98.

Acctually, I wouldn't upgrade from 98...  I only know of one person that likes XP, and ME just plain sucks!  2000 is alright, but it(along with XP) isn't compatable with some software and hardware.

But back to your problem, I'd say upgrading or reinstalling your OS would fix the problem, but there may be an easier way...