Then your best bet is the card I recommended.
AGP was a grapics hardware design from 2004-2005 that didn't work out. I built a system in Feb of 2005 and by the fall it was PCI 1.0.
Fortunately Radeon made some AGP cards when they came out with the 4000 series. They were good cards for their time but are dated now. This is now 2013 and based on your components I am guessing your computer was built in the end of 2004. You have had a good run but that machine will not run the newer games. 8+ years is a great run for a gaming computer. You neeed a new system.