In my honest opinion I wouldn't even bother upgrading it. Get a new motherboard, processor and new DDR3 RAM instead, otherwise your wasting money on a legacy chipset.
Let us know your total budget and what you use the system for and we'll recommend something that is suitable.
Leeky is absolutely correct here.
You are far better going for a brand new motherboard, not a majorly expensive one. You can buy one from this one last generation, or the generation before, and the AMD processors should be compatible for at least the next 6-8 months (if not longer). Get a new motherboard, make it a fairly good one. Get some cheap RAM and a cheap CPU. The key here is the motherboard - you can upgrade to a better CPU and RAM later on. Just give yourself a good foundation to build on later.
I believe a AMD Athlon II X2 260 on a ASUS M5A88-M EVO Motherboard should do the job well, and its not too expensive (AMD people, if I am wrong, please correct me - I am not big on AMD CPUs/Mobos).
The processor should be able to handle most games. Have a good look at your graphics card aswell, make sure its fairly up to date
Keep in mind these are Australian proces, but if I bought the CPU + Mobo + Low end GPU, it would cost me around $260 - you should be able t oget it much cheaper in the US.
And who are you gonna beleive a man whose been researching this for months or a man who just read your posed and researched it for day ! listen to me but if you want to upgrade your motherboard be prepaired to just buy a whole new pc !
BELLY888, please do not insult/flame others on the boards, it is demeaning, and completely unnecessary.