This is long, and 'Windy', warning you in advance.
The cooling provided for the laptop is the air that is drawn in.
The air cools the hardware components inside, to keep them to a specific temperature.
A small fan is used to draw the air in, and then the air goes to the cooling components inside.
The air that is drawn in picks up all kinds of foreign debris.
Dirt, dust, lint, hair, and even food crumbs.
Even if you are the best housekeeper in the world, the above mentioned foreign debris always collects inside your computer.
This foreign debris clogs the fan, and the cooling components inside the computer. The cooling capacity drops tremendously.
When it does the Processor overheats, and turns off.
[It's a Fail-Safe feature to keep the Processor from burning up ]
For this reason the inside of the computer should be cleaned, on a regular basis as needed.
I state regular basis as needed, because environments vary.
Some computers because of the area they're in need to be cleaned more frequently, than others.
1) Computer unplugged from power
2) Computer on a table, computer case open, observe Anti-Static Precautions
3) Use a can of compressed air for computers, and clean out the inside of the computer.
Also clean out the inside of the Power Supply the best you can.
The can of compressed air for computers comes with a plastic 'straw'.
The straw is inserted into the can of air's nozzle, and the lock tab on top of the nozzle is removed.
(Used for shipping)
Start at the top inside of the computer on one side. Pick whichever side you want.
Squeeze the trigger in all the way, and go across.
When you reach the other side, let go of the trigger.
You will be spraying air like a painter uses a spray paint gun.
Now drop down a row, and spray across again.
How far you drop down is up to you. You can see how the air spray is working, and can judge accordingly.
Keep dropping down in rows until you reach the Processor Fan.
For the Processor Fan use Short Bursts.
Squeeze the trigger in all the way, then let go quickly.
You do Not want to spin the fan faster than it was designed for.
This can lead to premature failure of the fan's bearings.
After you're done with the Processor fan, keep going down in rows until you reach the bottom of the computer case.
Hold the computer case at the top with one hand, use the other hand for the can of air.
Tilt the top of the computer slightly towards you, and spray the bottom of the computer out
A) Laptop on, and running, observe where the air is drawn in. It may be drawn in on the side, or up from the bottom. The vented grille on this air opening is the Air Intake Duct.
You want this duct.
You Do Not want the Exhaust Duct. This is where the hot air comes out.
B) ALL power removed from the laptop. Remove the AC adapter (Charger), and Battery.
C) If the Air Intake Duct is on the bottom of the laptop, tilt, and hold the laptop up at an angle with one hand.
Use the other hand for the can of air.
Put the straw against the Air Intake Duct's grille opening, use Short Bursts of air.
(Again, you do not want to spin the Fan too fast. If you hear it go > Z-z-z-z-ing, it is spinning too fast)
After you are satisfied that it is clean, sit the laptop down, wait 10 minutes.
Then reinstall the Battery, (First), and then the AC adapter. (Charger)
If the Air Intake Duct is on the side, use Short Bursts of air until you are satisfied it is clean.
Follow the above.
Sometimes using a can of compressed air will not work. The foreign debris is clogged in there so tightly, that the can of air cannot remove it. A computer repair shop has to open the laptop, and physically remove it.
The term 'Laptop' is a fallacy, a joke, for some laptop models.
If the Air Intake Duct is on the bottom of the laptop,
1) Your clothes,
2) Bedsheets, or blanket,
3) Directly on a couch,
4) On your lap,
5) Or sitting it directly on a carpet floor, will block the Air Intake Duct, and cause the laptop to overheat.
For laptops with the Air Intake Duct on the bottom, they should sit on a flat surface such as a table.
(Like a desktop computer. See the joke?)
Or on a hard flat surface on your lap.
You can use a cooling pad to help.
Example of a cooling pad,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4662503&CatId=3486
Some laptops have a poor cooling system. No matter how you treat the laptop it will overheat.
Laptops with an Intel processor, will run hotter than laptops with an AMD processor, before they turn off.
(And AMD processors run hotter than a comparable Intel! Sheesh!)
Just some ideas, and information. Don't shoot the messenger.