Hi, and welcome to TSF!
This is definitely overheating. Generally, laptop fans come on when you power the laptop on and turn off until the laptop gets hot. When you are in Windows, download MobileMeter from my sig and post the temps it displays.
You may want to invest in a cooling pad that will help cool the laptop. Here are two good ones:
http://www.newegg.com/Product/Produc...82E16834999336
http://www.newegg.com/Product/Produc...82E16835192013
The second one is a lot more comfortable on the lap.