Try rebooting into safe mode and at a command prompt enter chkdsk /r (trys to repair damaged or missing XP files).
I did a system restore back to a certain point a few weeks back but didn't get the results I wanted. I tried to go back further and it said it couldn't restore that point. So, I decided to undo my system restore back to the original point before I ran system restore. When I tried the undo command it ran and then froze on a screen without doing anything. So I rebooted the machine and now my computer freezes when it starts to run Windows XP. Anyone know how I can get my computer running. I can't even run Windows now.