I'm not really familiar with how to do this, the manuals for the motherboard might not be available (can't know since I'm at work now).
But, here is the RAM in the machine:http://www.newegg.com/Product/Product.aspx?Item=N82E16820145197
I'm guessing in the Bios will be setttings to just change to match this (from the newegg product page)?
This would be the motherboard:http://www.newegg.com/Product/Product.aspx?Item=N82E16813130136
I also should add that this is a recently happening problem when the PC is under pretty heavy load (gaming), and the PC has been working fine since 2008 with no recent hardware changes.