Laptop heatsink fans seem to collect a lot of dust due to their location.
I have an HP Pavilion and the website has repair guides avaliable in PDF format for you to download and read. Find the make and model of the laptop then check their website out.
Anyway, the repair guide for mines shows me how to disassemble the laptop so I can get to the motherboard and components. Take a can of Dust Off with a straw, stick it past the fan blades, and blow through the heatsink. You'll be surprised at how much dust builds up in there after four months. You can also remove the heatsink and throw some AS5 on; most laptops just have a sticky "gum like" thermal pad. Be sure to clean off the fan blades as well if they are clogged and add some oil to the bearings if you want.
Yep; that's a Delta Fan in there with a good layer of dust built up on the blades. Either I have a very dusty house or I should keep my laptop off the floor.
PS If you do remove the fan; don't forget to plug it back in. Last time I serviced my laptop, I forgot to reconnect the fan and realized that just right after I finished putting the unit back together. Had to take it apart again which was quite irritating considering that I have to remove about 20 different screws.