Go to the desktop, and right-click to bring up the properties window. Choose "Settings" and then hit the advanced button. Somewhere on the form that is brought-up (under "adapter"), you should get something that tells you what your card is. Post that back here.
Chances are that if your PC is older than 6 months, its not PCI-e. If its newer than about 3 years it will be AGP.
However, it may actually not be a graphics card at all - it might be built-in to the motherboard.