According to the internet, there are both pci and agp models of the 5200.

If you open up your computer to find out, an agp slot is usually off-set from the pci slots (closer to the edge). here's a picture for reference:
http://en.wikipedia.org/wiki/Image:AGP_slot.jpg

If it is PCI, your options are slightly more limited, though chances are you have an agp slot even if you aren't using it.