Video Card Upgrade Question

Hi there I am an EQ/EQ2 oldy but a computer upgrader newbie. I just
purchased a computer about two months ago and need to upgrade my video
card in order to play EQ2 but I have a question. I, apparantly, have
two pci slots available but when I have been looking at the descriptions
of various geforce video cards most of them say they need pci-express
slots ? I am not sure what this means: do I need to buy something else
in addition to the video cards to get them to work in my computer (in
the description of my computer it says "pci" slots, not pci express.) I
have a HP Pavilion Media Center TVPC, Intel Pentium D Processor 915 with
two processing cores. 2.8 Ghz. My "graphics" is Intel Graphics Media
Accelerator 950. Thank you !