If Windows XP won't boot normally, try one of these tactics:

Access System Restore from a Command Prompt

Here's how:

Press the power button, and gently tap the F8 key every half second or so until you see the Windows Advanced Options menu.

Use the down arrow key to navigate to Safe Mode--Command Prompt Only.

Press Enter. There may be a message or two.

When the black command panel opens, type C: and press Enter.

At the C:\> prompt, type cd C:\windows\system32\restore (Note the space between cd and C:\) and press Enter.

At the new prompt, type rstrui and press Enter.

System Restore will open and you can use it to restore the system to a previous state.

If the computer won't boot into Safe Mode--Command Prompt Only, you still may be able to use the

Last Known Good Configuration

Here's how:

Press the power button, and gently tap the F8 key every half second or so until you see the Windows Advanced Options menu.

Use the down arrow key to navigate to Last Known Good Configuration and press Enter.

Select Microsoft Windows XP (or Whistler Personal), and press ENTER.

Windows should start using the most recently created restore point.