A very valuable utility when you're trying to solve a major problem windows system restore.
A current copy of files and other important files in Windows 7 are saved and can be restored using System Restore.
Follow these steps for reverting important Windows 7 system files back to a previous state using System Restore:
1.Navigate to the Start -> All Programs -> Accessories -> System Tools program group.
Click on the System Restore program icon.
2 Click Next > on the Restore system files and settings window.