A M D Athlon processor xp repair

3 things can be here, dead monitor, dead PC, dead video card. So.. try a different monitor you know works, if that works, monitor is bad. If not, replace the video card, if it's replacable, if that works after that, video card was bad.

If video card or monitor don't fix things, your power supply may be dead, try a different power supply. If the power supply does not help, could be the motherboard, replace that and try again. If you have one of the original Athalon computers, probably not worth fixing it, just replace it and keep your old hard drive to copy data over.