Its your fan, its probably getting over worked. If that happens, get some extra portable fans, and just start blowing them on the underside of your laptop, that should help. Mine does the same thing, but it sounds like a disc is stuck in the drive, but its the fan, once i turn the extra fans on the laptop, in a couple minutes, it cools down and the noise stops. If that doesnt help, take it to a computer shop (if you can afford those expensive assholes) and have them look at it.