Starting your computer in Windows XP Safe Mode can help you diagnose and solve many serious problems, especially when starting normally is not possible.
To begin entering Windows XP Safe Mode, turn your PC on or restart it.
Just before the Windows XP splash screen shown above appears, press the F8 key to enter the Windows Advanced Options Menu.
Not a Windows XP User?
See How Do I Start Windows in Safe Mode? for specific instructions for your version of Windows.