I can't tell about this particular model, but in general the options are:
1. The hardware is kaput.
2. There is some problem with the drivers (look in Device Manager) or a necessary helper program
3. You switched wireless off (the socalled 'airplane mode', because wireless should be turned of in airplanes). That's either a physical switch or some software, usually Fn + a function key
On most laptops, there's a small LED showing if wireless is on or off. Does yours have one? What does it show?
My Acer lap-top (Aspire One D270, OS Windows 7 Starter) has stopped connecting to our wi-fi after working fine for about the last 4 months. It can't locate any networks (though my smartphone picks up the connection fine). Any help hugely appreciated!!