How to restore the operating system to a previous state in Windows XP

If Windows XP starts
1. Log on to Windows as Administrator.
2. Click Start, point to All Programs, point to Accessories, point to System Tools, and then click System Restore. System Restore starts.
3. On the Welcome to System Restore page, click Restore my computer to an earlier time (if it is not already selected), and then click Next.
4. On the Select a Restore Point page, click the most recent system checkpoint in the On this list, click a restore point list, and then click Next. A System Restore message may appear that lists configuration changes that System Restore will make. Click OK.
5. On the Confirm Restore Point Selection page, click Next. System Restore restores the previous Windows XP configuration, and then restarts the computer.
6. Log on to the computer as Administrator. The System Restore Restoration Complete page appears.
7. Click OK.

Troubleshooting
You may inadvertently restore Windows XP to a previous configuration that you do not want. To undo the restoration:
1. Log on to Windows as Administrator.
2. Click Start, point to All Programs, point to Accessories, point to System Tools, and then click System Restore. System Restore starts.
3. On the Welcome to System Restore page, click Undo my last restoration, and then click Next. A System Restore message may appear that lists configuration changes that System Restore will make. Click OK.
4. On the Confirm Restoration Undo page, click Next. System Restore restores the original Windows XP configuration, and then restarts the computer.
5. Log on to the computer as Administrator. The System Restore Undo Complete page appears.
6. Click OK.