depending on the generation of Athlon's it came from it is anywhere from a 130nm to a 65nm processor, however it is a single core at only 2 or 2.2GHz so that is likely your limiting factor in your system and cant pump out enough to your graphics card, see if you can increase the AA or AF and not take a performance hit, if you can it is your processor. If you have the budget to you may want to build a new system as you already have the graphics card which is a good chunk of the cost, $700 should get you a pretty good system.