ok.. first i would see if it a windows error.. meaning go into another os (DOS maby) and see if the problem is still there. if not, an easy solution for some would to just reinstall windows.. that is the "lazy" way of fixing your problem. or just search for people with the same problem (google).
question: in "disk managment" does it come up as a 600MB DRIVE or a 600MB partition?
question: Do you really need that information on that drive? is it original stuff ( eg: homework, etc) or is it a couple hours on kazza?
if your running Win 2000, XP and you just don't care about the info on the drive (and it is only coming up as a 600 PARTITION) just wipe the whole drive and get your space back. sorry if some of this was already covered...