Look on your motherboard and on your BIOS chip, and write down any numbers you see on it. Then run the numbers on the motherboard through Google. I guarantee you'll find out what your motherboard is with that, since one of the numbers on your motherboard should be the model number. Then all you gotta do is search for those BIOS numbers on the motherboard manufacturer's website itself. Most websites should have a site search function, otherwise use Google's site searcher.
That's how I found out what BIOS and motherboard I had on my old refurb a while back, it should work for you too.
