1) Your computer becomes very slow after booting up
2) Your computer may crash, blue screen or completely lock up
3) Your computer may randomly reboot

What can be done to diagnose computer over heating?

Easy way to check CPU temperature
There are a few ways to check if your CPU is overheating.  The first and most un-intrusive way is to reboot your computer then go into the bios (usually hitting the F2 or DELETE key when your system reboots gets you into the bios).  From there you can go to the menu item called status or diagnosis, not all BIOS will have this feature, if your system does not have this feature move to the next step.  General CPU temperatures are under 70 degrees Celcius (Please see the CPU Tempurature chart for more info)

Physically checking if the CPU is overheating
The best way to do this is opening up the case of your computer and locating the CPU, you should note that proper grounding (with an grounding strap) is recommended always when working on PC components.  Boot up your PC and bring it into the BIOS, you can then let it run for a few minutes and then touch the CPU heat sink (its the big metal thing with a fan on it).  If its to hot to touch then most likely your CPU is over heating.

Other things to check in your computer
You can check other things in your computer when over heating.

1) Check that all the fans are running
2) If it is dusty or there is a build-up of dust on the fans and other components then you should get a dust blower or vacuum to remove the dust
3) check the CPU heat sink compound, if there is not enough compound or the heat sink comound is dry/flakey then it needs to be reapplied.

Article written by MyComputerAid.com

Post from: MyComputerAid.com Computer support

Symptoms that your computer cpu is over heating