If you run that mobo cpu combo you'd also need a ram upgrade :D

Imo best thing to do is unless you just hate that mobo like nforce diver problems with windows 7 or something is to upgrade the cpu using an old c2d or c2q assuming that is lga 775
I'd just look at what your max fsb is on that mobo and shoot for a cpu around there toss in some money to get 4 gigs or ram spend all the rest on a gpu assuming you have a good power supply to do so. ofc the issue you might run into is if you're not carful about selecting your cpu is that it wont work on your mobo and then you'll just have spend 100 bucks on a cpu you can't use.