I would give the inside of the case a blowout with compressed air. When blowing air through the fans make sure that you physically stop them from spinning, as they may generate power and blow something up. Remembering to ground yourself by placing the back of your hand on the Power Supply Unit or a metal part on the PC and not moving your feet. By not taking this precaution it is possible that you could inadvertantly cause damage to the PC from an electrostatic discharge. Then remove the Heatsink, giving it a thorough clean and reseat the CPU applying new CPU grease. If the Fans spin freely when you give them a spin they are probably OK. If there is resistance replace them.
Clean the Cooling Vents
Depending on the model, vents can be found on the side, back, and/or bottom of the notebook PC. These vents allow air to flow through the PC and keep it cool. Buildup inside these vents impedes the cooling process.
Clean I/O Ports
The back of the notebook PC has a series of ports. After cleaning the cooling vents, take the compressed air and blow out any debris that may have accumulated in and around these ports.
Clean the golden edge of each memory stick with a soft rubber/eraser, remembering not to touch the golden edge of the memory stick. Check with one stick at a time, remembering to disconnect the power from the PC.
Keep us informed as to your progress if you require further assistance. ;) :D
