Reading http://support.microsoft.com/kb/330182 you have to have your bona fide XP CD and be skilled at copying files and more COMMAND LINE work than I can teach here.

But the errors remind me of a remote control trojan I've been removing this last year. No, Norton didn't protect them.

My advice? Slip in a new blank hard drive for a test install of the OS. Hope it's ok and then get your files off the old drive.
Bob