Just upgrade the CPU or mobo/gfx as well?

[mmcookies]

i doubt that your board would be able to go to 4gb, you might be stuck at a 2gb limit, as for GFX card you could look into getting a ATI Radeon HD 3850 Pro 512MB or 1GB (one of the highest spec cards you can get for the AGP slot) they are not that expensive (but then nor is buying a new rig nowadays 8o )

Thanks for the tip on HD3850.

I've looking at the listings from my supplier... looks like I might be able to get pretty much a new computer for under 400 Canadian (353 USD).

Intel Core2Duo E5300
Asus P5GC-MX/1333 S775 945GC Chipset
2gb of ram
ASUS GEFORCE EN9800GT HB HTDI 512M PCI-E DDR3