Well the good news is that your case will accept a standard "micro-ATX" motherboard. An Asus P4S533-MX board will fit, will support your CPU and RAM, and will give you an AGP slot. I sell them for about $90.00 Canadian, so you should be able to get one pretty cheap in your neck of the woods too. Refer back to my original advice, find a local shop to supply the board and video card, install them and make sure they are running right.

Oh, and I almost forgot....don't buy computers at Wal-Mart! Toilet paper yes, computers no!