My old PC didn’t even have an AGP slot, but it did have older PCI slots (NOT PCI-Express).
I brought a Nvidia FX 5200 128MB PCI card for about £50. You can get them even cheaper now.

This was a brilliant card for the money, and returned constant frame rates in the lower 20’s.

🙂

It seems that this is the case with my computer. Its about 6 or 7 months old and doesn’t have AGP or PCI-Express. It does obviously have PCI and I managed to track down a decent enough card for £65 – 256mb, too. 🙂