Overclocking A Phenom II X4 830

Just some background information, I've overclocked before a few times, mostly in intel K processors (so pretty easy) and I've always done it through the BIOS. What I need help with today is quite different. My roomate wants to get into PC gaming after watching my play BF3 on ultra, and lamenting the graphics on his Xbox 360 (LOL). He's willing to spend some money now to upgrade his prebuilt computer (http://deals.woot.com/deals/details/25143d23-3a73-47e1-...) that's what he currently has. I reccomended he get a new GPU and PSU. That being said, I bet his processor could seriously benefit from an overclock. However, HP has a locked BIOS, and the processor itself is locked so I would have to mess around with the FSB to change the clocks (I think, never done that before).

My question for you guys is, because I can't access the BIOS and the processor is locked, how can I overclock it, and is the overclock it even worth it? Is the processor complete *** and will just throttle his new GPU (thinking a 660ti or 7870)? Also, I do have a coolermaster 212 that I am willing to let him have. Let me know what you guys think, thanks!