Is there a game in particular you are attempting to play?
It's hard to recommend if we don't know the purpose.
Assuming you want a PCI (not PCIe) video card, this is about the BEST PCI CARD you can get:http://www.newegg.com/Product/Product.aspx?Item=N82E16814161353
You can browse the other "PCI" cards yourself. This card is TWICE as much money as a similar PCIe version but prices on older tech are often higher.
There are a few games you might be able to play with this card and your machine, but obviously nothing high-end. You could try installing this card and running some DEMOS to see what you can get.
You could try Torchlight though I'm not sure if your CPU would be good enough or not.
There are other types of games though, such as Angry Birds which would work fine...