Depending on the laptop, you can unlock them fairly easily. I know there are some high-dollar laptops that are already OCed out of the factory, but locked there. However, I advise you to not try. As Hef said, you would be struggling to cool that thing.
EDIT: Hef, every time I read your sig, it takes me back. Haha, such a great series. btw, I know we've already had this conversation.