Windows related problem.

[Tenshi]

well you should try ctrl+shift+esc (same thing as ctrl+alt+del to bring up the task manager I use the ctrl+shift+esc because i changed the way user login so ctrl+alt+del you can lock the screen and such for me) and execute 'Explorer'
You might also want to have gone back to your previous setting (like using norton ghost (hate symantec)) or the backup feature that is on windows (which is suggested to be used on a regular basis (scam to make more moeny on HDs I bet))
other than that you might (if you can) want to back up what you want/need off your PC and reformat and reinstall everything