MacBook, Fan always on? - Fix this problem here.

My Dad's Mac's fan has been on constantly for the past few weeks for doing little tasks such as emailing, I decided to fix the problem by resetting the SMC (System Management Controller).
If you have a similar problem this is how you solve it:

Firstly turn your computer off.
Then disconnect the power adapter and remove the battery.
After that press and hold the power button for 5 seconds and then release the button.
Then reconnect the battery and power adapter.
Then press the power button to restart the computer.

This resets the system management controller.

I hope this helps you solve the problem.