well all p4s that i have seen use ddr ram. I guess you could look to ebay and find a couple 1 gig sticks of ddr400. Chances are your board has an AGP card. Those are hard to find but there should still be AMD 3000 series around. You can get an AMD3450 for a low end or a AMD3850 for a high end.
To be honest those parts are sort of hard to find now and as a result they cost alot. I would just save your money and rebuild with a new chip ram and mobo.