I have seen 3 different makes of laptops which are more than a year old sometimes overheating
or that the Fan is buzzing Alot stronger than it did in the begining.
This is probably because of the dust build up in the vents.
This trick seriously solved the problem
either get a can of compressed air or a vacuum cleaner and push or pull out the dust from all the vents.
with the compressed air you will seriously see alot of dust pushed out.
It worked on all three laptops