This is what happens when you run your laptop (or pc for that matter) in a dusty environment, or if the person you bought it from (in my case) has done so.
Needless to say it's not doing a thermal shutdown as readily anymore, took me a good hour or so just to take it apart without breaking anything.
And yes i could have used compressed air to do it, but i had actually taken it apart to fix a known problem with the power socket (good on ya Toshiba!!) which has been the subject of a class action suit in the states.
For those wondering its a Toshiba Satellite A70.