Re: im buying this comp...
what is your mobo brand? Most mobo manufacturers will give you windows based applications to upgrade your BIOS. Also if this isn't an INTEL Mobo, then you should be able to overclock it by going into the BIOS. Just dont get excited and overclock it by 50%, you'll fry everything including your tongue :p
Just start by 1% and slowly increase it with each reboot if you have not noticed any stuttering, windows crashes or BSODs. Once you start seeing those, you know you've overdone the overclocking.
if you get deeper into overclocking, just dont only bump up the CPU clock speed, overclock the ram by adjusting the timers (based on the RAM brand you have) and gradually start bumping up the voltages too. But make sure your computer is well cooled else you will see crashes from very early in your overclocking endeavors.
Just a reminder that overclocking WILL kill the life of your CPU. If the silicon continues to operate at higher than normal temperatures on a regular basis, there is a point after which it will just not perform the same number of calculations as compared to when it was new.
I have a 3.2ghz Northwood architecture CPU that is sitting in a box because after constantly overclocking it, it has a miserable vista performance score of 1.8 but a cousin of mine who has the same cpu has a vista performance score of nearly 3.0