Upgrading my computer what part should I do first?

It's usually cheaper to buy a new pc than to upgrade more than 2 or 3 components. You can get a dual-core with 4 gigs ddr2 ram for 400 dollars then add a decent graphics card. Also sell your old pc for about 175 dollars to help buy the new pc. Look at Fry's.com. AGP is old and slow. Pci express is what's good now.