If all you want is Shader Model 2.0, then something like a 4350 AGP (your computer only supports AGP cards, not PCI express, make sure you buy the AGP card) would do fine, but if you want some real performance, a 4650 AGP or 4670 AGP would be pretty good. I wouldn't spend too much, though, because that computer is really outdated... Its processor is quite weak and with only 1GB of ram, it wouldn't be worth buying too good of a card.