AKM880 :
+1. And you can try ClockGen, stuff like that. Just remember to watch thermals and stress test. Go slow, don't go with a huge o/c at once.
We shall never forget that the user of that PC is not the OP, but his neighbour's 8-year old kid. I'd stay away from overclocking a system that isn't mine unless the owner agrees to it and fully understands the risks.