I would try a better power supply. Get one with a large single 12v rail, around 50-60 amps. Corsair and pc power and cooling are the best brands, followed by seasonic, enermax, ocz, and antec. You can also download the newest driver off amd's website for your current video card. Then uninstall your old drivers in the "add/remove" section of the control panel, reboot, and install the new drivers. If this doesn't give your gaming more stability, you can go with a faster video card or new system, and use the power supply in your next system. Oem systems don't come with good power supplies for gaming.