How do you find out if your video card is AGP/PCI/or something like that?

Im trying to buy a new video card for my computer, but i dont know weather my old video card an ati radeon 7000(Yeah i know its old :P) can be replaced by a new video card. what im trying to say is i dont know wether to buy PCI/AGP/ or sumtin liek that to replace it with so i want to know how to find out which is compatible