How can I tell if my computer takes PCI or AGP video cards?

I need to have one of these types of cards to play fallout 3 - a href="http://pastebin.com/m10d00ee3" rel="nofollow"http://pastebin.com/m10d00ee3/a - and I'm looking to buy a new video card buy I need to know whether my computer is AGP or PCI (or PCI-Express) how can I tell?