Might not be a dust issue...fan could be dead. Make sure it's blowing air out the vent first of all. If it is, proceed to the compressed air method. Preferable if you take it apart to do this though, otherwise you're just blowing giant fuzz balls around inside. At minimum, undo the covers for the RAM and HD slots and take those out before you start blasting, just gives another inlet and outlet to blow in to or get dust out of. As far as temp monitors go, Google CoreTemp...it's free. Good luck, laptops are a pain in the a**.