How to Use the F11 Button for System Restore
Windows XP contains system recovery information, including the operating system, device drivers and software required for a complete system restoration, in a separate partition on your hard drive. You can set your operating system to create regular "restore points" so that you can roll back your system to a certain date. System recovery can be completed through a set of CDs or DVDs that you create, or directly from the restore partition by pressing the F11 key during system bootup.
Start your computer.
Press the "F11" key within the first three seconds of the boot process.
Click either the "Non-Destructive System Restore (Recommended)" option or the "Full System Restore (Destructive)" option.
Follow the prompts to restore the system.
Restart the computer when prompted.