Yes, it's called flashing the BIOS. I assume you have a prebuilt computer, and you want to overclock it, but you can't find the setting. Well, most manufacturers (HP, Dell, Compaq, Gateway, etc.) use BIOSes that don't have settings for this. Most likely, this is because they don't want the average user to screw anything up, then get them in trouble for it. Anyway, in most cases, it's not possible to do it. In some rare cases, it's possible, but for most users, you cannot overclock a prebuilt computer.
If you don't have a prebuilt computer, what kind of motherboard do you have?
C2D E6600 | 4GB DDR2-800 | 9800GTX+ | Asus P5B-E | 150GB Raptor | 320GB 7200.10 | 750W Xigmatek PSU