yep, seen this happen a few times on my dad's XP machine.
Just create a new account, copy all the folders, and you should be basically up and running again. Some things will need to be redone. Big pain in the butt if you ask me... you think they could have a utility for repairing profiles or something.
Anyway, seems to happen more often if the machine is crashing, or not being shut-down properly, so try to avoid those.(haha, like we don't always try to avoid crashes anyway, right?)
dragonb