If the above doesn't work, try using system restore.
1. Restart your computer, and then press F8 during the initial startup to start your computer in Safe Mode with a command prompt.
2. Log on to your computer with an administrator account or with an account that has administrator credentials.
3. Type the following command at a command prompt, and then press ENTER:
4. Follow the instructions that appear on the screen to restore your computer to an earlier state.http://support.microsoft.com/kb/304449/
Use a date from before the problem first began.