If you want to use the old case you'll need a micro-ATX motherboard. Since the socket is a few years old you're kind of out of luck unless you're okay with buying from eBay. The best thing to do though is accept ForeverLavenders mobo if he can find it and buy a new case; something like a Corsair 200R should do the trick. His overclocking board is far superior to the underengineered OEM crap that came with the computer.
Oh and btw, what kind of power supply do you have? If it's of extremely poor quality it could have killed the motherboard prematurely.
