What does this fan button do on my laptop?

I bought a advent 7113 laptop with vista on it and there is a button next to the standy button with a picture of a fan on it.when i press it i cant see what it does apart from a light that comesand ideas is it to cool the cpu and do i have to press it and if so when?there is no info in the blokeual that explains what this button is for
Answer
Are you sure it looks like a fan and not like an antenna with radio waves going out? cause if it looks like that, then it might be the button to activate your wi-fi receptor. i believe the advent 7113 does have wi-fi built inedit: does it kind of look like this?http://www.zdnet.nl/images/nw0406/040610_wifiboost_kl.jpg