Hmm i think it is better to save money to build an entirely new rig,a 2.Xghz dual core cpu won't able to handle current and future games or atleast it will be unenjoyable,well if you really want to play some games on your pc badly,you can get a cheap hd 6670 card or if you want to you can get a gtx 750 ti which doesnt need a new psu and great a mid gaming performance then work your way through a new mobo,cpu,psu,memory,hdd/sdd,case and transfer the gtx750 ti gpu on your new rig.