Your
mobo does have a socket775 but according to Intel it only accepts Pentium D and Pentium 4 cpu's. The fine print on the bottom of the page states using anything else may damage the board. This
mobo also has onboard video so unless you have installed another video card it also could be slowing down your games. If the games worked before and have since slowed down it would probably be because the hard drive is getting full and defragmented. Perhaps someone else here will know more.