Warning:
Use the following guide at your own risk. Overclocking your processor is not for everyone, and you assume all liability for your hardware when you make changes to it's functional settings.
Here is a great guide from Anandtech on how to quickly and easily overclock your QuadCore or Core2Duo processor.
Remember!: Heat is thy enemy, and you cannot expect to achieve the same overclock levels you read about if you're using the stock HSF in a case with 2 fans....
Anyhow, on to the guide!
http://forums.anandtech.com/messageview.aspx?catid=28&threadid=2057083&FTVAR_STKEYWORDFRM=&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear