Here are a few tips to try as well.
Go to an electronics store, and get some heat sink paste. Open your puter, carefully remove the heat sink from the CPU, and clean the old paste off. Replce with new paste ans reassemble. Clean out the heat sink fins as well, and the fan blades
Next, remove your memory modules and give the contacts a rub over with a soft eraser. Clean off with an isopropyl alcohol spray and refit.
Do the same with the video card if one is fitted.
This may not fix the problem, but it sure wont hurt.