>What does the fan on the back of the computer have to do with CPU usage???
It's quite simple. When the CPU usage is high, it generates lots of heat. When there's lots of heat, the fans kick in.
That is absolutely STUPID.
A CPU doesn't generate any more heat when it is being used more.
It's not like an auto engine. The same parts in it are always powered up and operating at the same speed, whether it is busy or idling. The parts are still being used just as much when the CPU is not "busy." They sit there wasting time with thumbtwiddling operations in Windows at the same high speed, waiting for the user to do something. And the RAM is also running at the same speed.
Disk drives and CD burners are the only parts inside the computer that produce substantially more heat when they are used. And some video cards produce slightly more heat when the image is complex.
The only time a CPU "slows down" is when a laptop goes into power-saving sleep mode. And of course, it stops when you turn off the power.
The factors that most determine how often the fans run are the room temperature and how open the space around the computer is.
Also, there should be quite a delay between any increase in heat generation and the time the fan comes on, because it takes time for the heat to get …