System Restore is an extremely helpful tool built into Windows XP and Vista. System Restore runs in the background as a service and continually monitors system-critical components for changes. When it detects an impending change, System Restore immediately makes backup copies, called restore points, of these critical components before the change occurs. In addition, System Restore is configured by default to create restore points every 24 hours.
To use System Restore, first restart the computer by pressing [Ctrl][Alt][Delete]. When you see the message Please select the operating system to start or hear the single beep, press [F8] to display the Windows Advanced Options menu. Now, select the Safe Mode item from the menu and press [Enter].
Once Windows boots into Safe mode, click the Start button, go to All Programs -> Accessories -> System Tools, and select System Restore. Because you’re running in Safe mode, the only option on the opening screen of the System Restore wizard is Restore My Computer To An Earlier Time, make sure it’s selected and click Next. Follow along with the wizard to select a restore point and begin the restoration procedure.
Confirm the date and time selected and click Next. Windows will perform the restoration and shut down. After the restoration Windows will restart and inform you that the restoration completed successfully. Click OK to continue the startup process.