Azn Cracker :
If you need to buy another motherboard. It is not worth it. What you might be able to do is buy a used core 2 quad if your current mobo supports it and forget overclocking. They don't cost much more than a motherboard and you will get a much larger performance boost.
True, but this old tech is cheap anyway. New motherboard + core 2 quad = $80 maybe. Let's not get too far off topic though.
If he wants to do this, he can pick up a cheap motherboard from eBay for around $30 or he can get a decent one for maybe $50.
Edit: I'm going through these on ebay, be careful what you bid on. This old tech is very particular. Many 775 boards either don't support overclocking or don't support the series of processor you have.
Anyway, this is all getting a bit off topic. The only way you can accomplish OC is to buy a new board. You can get a Core 2 Quad if you want better performance overall (which I would suggest anyway). There may be a slim chance that there's a BIOS version you can flash it with that'll allow OC, but we don't know what mobo you have.