Hi,
If you have a PC straight from a manufacturer they mostly disable any OC features from the BIOS to prevent any damage, if this is the case you will more than likely need to purchase a aftermarket mobo.
As far as im aware, there is no sofware that you can use to actually overclock the CPU from within the OS, only monitor and stress test. You have to use the BIOS to change the FSB speed/multiplier!
I only really dabble in OCing so someone with a bit more experience may be able to help you more!