OCCT (OverClock Checking Tool) tests the stability of your computer.
It will launch heavy calculations on your CPU, and check the results. If there are any errors, OCCT will report it : it means your computer is unstable. It will put your computer under heavy load, and it will generate a lot of heat. Your CPU temperature will most likely be high, and thus you can check how well your computer's cooling is performing.
||Requires LiberKey portable application suite.