Hello Cerebralcow,
You would be incredibly lucky just to find any motherboard with DDR2 AND an AGP slot. Let alone with a certain CPU socket. AGP is pretty much a phased out technology. They still sell AGP video cards for people with older motherboards. But you will have quite a hard time finding new motherboards with an AGP slot. I checked Newegg for any DDR2 533 boards with an AGP slot and I came up with your same conclusion....nothing. I didn't even look for a specific socket type.
However, I notice you call it a 16x AGP slot. AGP comes in 2x, 4x, and 8x varieties. 16x typically would refer to PCI-Express X16. So I checked Newegg for the 7800 video card and couldn't find a model that came in an AGP version.
Are you sure your card is AGP? If it is an AGP card, my advice would be to replace your video card. Well regardless of my advice, I doubt you have any choice either way.
Hope that helps
