My laptop keeps shutting off.

For some reason my laptop automatically shuts off whenever I do anything CPU intensive. I think it might be a problem with overheating. When I feel the back of it, it's ridiculously hot. Right now I am solving this by underclocking using the power consumption utility. How do I fix this?

sell your laptop and buy one that doesn't suck.

Is it under warranty? Send it in for repair. If it's not under warranty then it's old and you should follow 2:s advice

Clean the gunk and fluff out of the CPU heatsink. If it has an easy access panel, good. If you have to half-dismantle the entire laptop to get at it, don't attempt unless you know what you doing.