[Arryn]

Try loading XP in "safe mode". This will bypass your card-specific video drivers and use Windows' own standard drivers. If this works, you can then try messing with settings, or re-installing drivers.

BTW, since you have XP a bit of advice: always create a system restore point prior to changing your hardware config or making any drastic changes to the OS environment. Microsoft has an excellent metallic blue and black -colored paperback tome (ISBN 0735613826 $45 list) called Windows XP Inside Out that I highly recommend. It has pretty much everything you'll ever need to know about the OS.