Buy some thermal paste. MX-2 is good. Take off the heatsink, clean the heatsink and processor with alcohol (rubbing alcohol works), and blow things off with compressed air (or make sure there is no lint or dust on either surface as you can). Apply a small (bb sized) amount in the center of the processor. Reinstall the heatsink.
Just take the computer apart to find the smell. Usually all you need is a screwdriver.