His card is alright for gaming (wouldn't expect much with agp and that card though)
http://ati.amd.com/products/radeonhd2400/specs.html
Anyhow think I solved it for you. It seemed to be a driver issue with ATI, they released an agp hotfix for 2000 and 3000 series cards.
http://support.amd.com/us/kbarticles...AGPHotfix.aspx
as far as i understand the hotfix is drivers (so no installing drivers after it).
Another solution is to try the 3rd party omega drivers and see if that works
http://www.driverheaven.net/windows-...ows-xp-2k.html
If none of that works then you may have a defective video card.