Compaq presario cq160 overheating with just typical use; it overheats from the top right hand bottom. When it overheats, it turns off. We have uninstalled and reinstalled the OS - Windows XP, but still doesn´t help. Any suggestions?

Overheating When the CPU overheats then it will shut down (i.e. thermal overload) and won't boot up again until it has cooled down. If this is the problem is not fixed then the CPU will eventually fail.
A faulty fan causes the problem or the fan and heat sink assembly are clogged with dust.
Check the CPU fan to see if it spins freely, if not replace the fan.
If the fan and heat sink is clogged with dust the remove the dust and make sure the vents are clear and dust free. Use a small brush and can of compressed air to do this.

When the CPU overheats then it will shut down (i.e. thermal overload) and won't boot up again until it has cooled down. If this is the problem is not fixed then the CPU will eventually fail.
A faulty fan causes the problem or the fan and heat sink assembly are clogged with dust.
Check the CPU fan to see if it spins freely, if not replace the fan.
If the fan and heat sink is clogged with dust the remove the dust and make sure the vents are clear and dust free. Use a small brush and can of compressed air to do this.

Hi. Thanks for your question.
My first guess would be that your laptop is overheating. To confirm this you could download program called speedfan using this link http://download.cnet.com/SpeedFan/3000-2094_4-10067444.html please click donwload and once downloaded install on your computer.
Once you have this program you can monitor your computers temperatures and see if they're rising before laptop shuts down.
Laptops often overheat while being used on beds, carpets or any not flat solid surface. This causes air vent at the bottom of laptop to be blocked. That vent is crucial for laptops cooling. The other reason for laptop overheating could be dust and dirt that clogged any visible vents. Removing dust is fairly easy and can be done with little paint brush and can of compressed air which can be bought from any computer shop and some supermarkets.
I hope this helped you to understand your problem better. Please do not hesitate to ask more questions if this is needed. Thank You for using FixYa

This is rather LENGTHY and detailed dhivi, advising you in advance.

All of the components for a laptop are crammed inside a tiny box with a poor cooling system.

The cooling system consists of a small fan and Heatsink. (Fan/Heatsink Assembly)

The Heatsink Assembly is shaped like a U for the Compaq Presario CQ40 series.

The U shaped Heatsink Assembly is composed of a finned Heatsink, Cooling Tube, and metal plates (2) attached to the Cooling Tube.

The finned Heatsink is on one end of the Cooling Tube, with the 2 plates of metal spaced around the Cooling Tube away from the Heatsink.

The 2 plates of metal sit on top of the Processor, and graphics chipset.
One on the Processor, one on the graphics chipset. (GPU. Graphics Processing Unit)

The Cooling Tube is a hollow copper tube slightly flattened, and filled with Nitrogen gas.

Heat is absorbed by the plate on top of the Processor, and plate on top of the graphics chipset, and transferred to the Cooling Tube. The Cooling Tube absorbs the heat, and transfers it to the finned Heatsink.

The Heatsink then radiates the heat away. Air flow from the fan flows through the fins of the Heatsink, and helps carry the heat away.

Underneath the two metal plates is a thermal medium.
For the processor, Compaq used Thermal Paste.
For the graphics chipset they used a Thermal Pad.

Below is a link for disassembling a Compaq Presario CQ50, CQ60, or CQ70 series laptop.
VERY similar to the CQ40 series,

(Your laptop is one of the Compaq Presario CQ40 series of Notebook PC's. The exact Product Number is on the bottom of the laptop in a white Service Tag. P/N = Product Number)

http://www.insidemylaptop.com/remove-motherboard-from-compaq-presario-cq50-cq60-cq70-laptop/

Scroll down the page, and view Steps 20 and 21.
This shows you what your Fan/Heatsink Assembly looks like.

(Also a good guide for disassembling your laptop)

In Step 21 you see the Fan/Heatsink Assembly removed.
Looking at the two chipsets on the motherboard,

1) The Rectangular chipset on the Left, is the Processor
2) The Square chipset on the Right, with the purple diamond in the middle, is the graphics chipset

The purple diamond is a Thermal Pad.

In my opinion a Thermal Pad is junk.
Thermal compound (Paste) is interweaved in the fabric of the Thermal Pad.
Thermal paste dries up after being repeatedly exposed to heat.

This is why the top of the Processor, and bottom of a Heatsink on a desktop computer, needs to be cleaned off, and new Thermal Paste applied every so often. The Thermal Paste dries up, and loses it's conducive properties. (Even if it's Artic Silver 5)

Primer:
The top of a Processor, and bottom of a Heatsink are not perfectly smooth. A microscopic view would reveal, 'Pits, Hills, and Valleys'.
This imperfections create air pockets when the Heatsink sits on top of the Processor.

Air is an Insulator, not a Conductor.
Thermal paste fills these voids, (Imperfections), and is an excellent conductor of heat.
It helps transfer the heat from the top of the Processor to the Heatsink.

Same thing for the two metal plates which sit on top of the Processor, and graphics chipset in a laptop. The top of the Processor, and the top of the graphics chipset are not perfectly smooth.
Neither is the 2 metal plates which sit on them.

The Thermal Pad has dried up, and is allowing the graphics chipset to overheat.
This is what causes the lines you see in the LCD screen.

The Thermal Pad should be removed, and the top of the graphics chipset Thoroughly cleaned.
Also the top of the Processor.
The bottom of the two plates of metal should also be Thoroughly cleaned.
Then new, fresh Thermal Paste should be properly applied.

The Thermal Pad can dry up in a laptop in a years time.

To add:
The graphics chipset is surface mounted to the motherboard.
The Processor in a Compaq Presario CQ40 series Notebook PC is an Intel Core 2 Duo T7300.

http://en.wikipedia.org/wiki/List_of_Intel_Core_2_microprocessors#Dual-Core_Notebook_processors

The processor socket is a Socket P.
The processor has the pins, the Socket P processor socket has the socket holes.
478 of them.

http://en.wikipedia.org/wiki/Socket_P

The mounting of the graphics chipset is a surface mount called BGA.
Ball Grid Array

Instead of pins on the bottom of the graphics chipset there are solder balls.
The surface of the motherboard has matching Copper Pads.
The graphics chipset is set on the motherboard's copper pads, and heat is applied.
The solder balls melt, and solder the graphics chipset to the motherboard.

With constant overheating due to the thermal pad has dried up, or due to overheating in general, the solder joints start to melt, and the graphics chip loosens from the motherboard.
This causes a poor connection, and the results may be what you are seeing with your laptop.

This is one solution for that particular problem,

http://www.youtube.com/watch?v=bnkQNmKauEc

This is another solution,

http://www.youtube.com/watch?v=vR8L3B3eDr0&feature=related

This is the download page for the Service Manual (Free) for the Compaq Presario CQ40 series of laptops.
I chose the Compaq Presario CQ40-200 CTO Notebook PC, but the Service Manual is for all of the CQ40 series,

http://h10025.www1.hp.com/ewfrf/wc/manualCategory?lc=en&dlc=en&cc=us&lang=en&product=3767562&

Click on the file name >
Compaq Presario CQ40 Notebook PC - Service and Maintenance Guide
After you click on the link it may take up to 30 seconds before you see the first page, and addional time for the PDF file to fully download.

Regards,
joecoolvette

1) is the fan still working?
2) Turn the computer off, remove the bottom cover and clean up the inside by blowing compressed air into it. Be sure to remove all the dust and lint you see. Check the fan moves easily.
3) replace the bootom cover and try again
4) DO NOT use your laptop on top of a soft surface. That means no pillows and no blankets or any other type of fabric under your laptop. Do not use it on top of your bed either. Only on top of HARD surfaces.
5) Avoid playing any intense 3D GAMES. Most laptops are NOT designed for game playing

This is a compicated problem. First when it boots enter setup by pressing the F10. Once you are in set up reset all settings to default. Save changes and exit CMOS. If that does not help the situation have someone make you a boot disk, reenter setup and put the floppy as the first boot drive and then CDrom. Insert the boot disk, follow the instructions to boot. Once you are up and running try to roll back the computer to the last recovery point that worked. If that does not work you may need to see a local repair tech.

is this happening with the AC adaptor connected?
Connect the AC if it still is exibiting the same chariteristics Charging system needs to be addressed. If not then your batteries are weakening!

you are suffering from the famous overheat problem with these computers clean your fan as your video chip is overheating

Typical reasons could be overheating and or the charger is on it's last legs. Do you have the same problems when you're using the computer with battery alone. Does the laptop feel hot?

The reason the charger is getting hot is because it's probably a 65W charger and not a 90W (that's just a guess though)

Let me know if I'm right or not.

look at the back of the machine, there should be 2 screws top and bottom on the right hand side, unscrew them and the side panel should slide off revealing the computers inards