Well, this started both with my dead xbox and dremeling it in half and when I recently took my ibook apart to take the thermal pad off and replace it with thermal paste (Funny, I thought it would have thermal paste already). Well this failed because I didn't tighten the heat sink on enough with the two adjustable screws. Long story short, I haven't been able to get it back apart to fix it as I lost my key key O_o. I then just had a brilliant idea of using the xbox heatsinks to add cooling and since they already had sticky thermal paste on the bottom, I figured, why not, my laptop sits on my desk all the time anyways. <------ Special note to that, if you plan to be using your laptop other than on a desk most of the time, I would recommend you get a commercial cooling pad or the such that has fans in it and plugs into your usb port. This is just simply a quick and easy mod that's easily removable in the event that you need to move your laptop or go somewhere with it.
Step 1: What you need
Well of course it will help to have your savored ibook or macbook which ever, it should work on both I'm hoping. And most likely and large to medium and a small heatsink will work, I wouldn't recommend using thermalpaste, like the regular stuff as it is too messy, if you have to use sticky tack it works fine.
Step 2: Let's get started
Now, I am not responsible for anything you might do to your ibook or yourself. You shouldn't be able to mess anything up but MAKE a mess. To start, I'm using my ibook as an example. Start by removing the keyboard, there is two tabs at the top left and right corner of the keyboard. You may also have to "unlock" the keyboard using a small flat screwdriver and using it on the small screw beside the num lock button.