In the BIOS, under CPU management or something like that; there should be an unleashing mode or something like that. Turning that on will open up a new list below it, where you can enable extra cores. This I know for sure is how Asus does it. Other mobos, I'm not too sure. So it isn't too difficult if you built it yourself or had someone else build it. But if you bought it from Dell or HP or any company like that, you will not be able to.
Benefits:
There's plenty of programs out there that can't work with an odd core, so some programs will only work with 2 of your three cores. Unlocking the fourth core gets better results from those programs.
Overall better performance.
Risks:
Overheating; a good aftermarket heatsink puts this risk to shame
Instability; this is by chance. The three cores are built about the same platform as the four cores, but sometimes they don't meet the same testing standards. I have a dual core that is unlocked to quad core. Your odds have having stability is good.
Overall, if you have it, it's worth giving it a shot. But if you're banking on unlocking it, don't count too hard on it. If you can live with three cores go ahead, but if you're really itchy for four cores, I'd stick with the sure thing. Again, you need to have built the computer. If it's Dell, Compaq, Gateway, eMachines, HP, Lenovo, or pretty much any laptop, you won't be able to do this.
