I wouldn't try overclocking your store bought system. The bios probably has no options for cpu voltage, fsb, etc that you will need. I would either sell your system and start over, or just get a premium video card to boost your performance. The radeon 8500 oem is a great choice for performance/value, and sell for $100-140, depending on features. Read them carefully, as some features, such as tv-out, may be disabled on cheaper versions.