My lenovo laptop z580 wireless internet has stopped working?

My laptops internet icon has changed to a computer with an ex in the corner i'm currently using my Ethernet cable to use the internet how ever i have tried rebooting and nothing seems to be happening i have had my laptop for about 2 years what should i do to fix the wireless internet?

Things that COULD be wrong with it (diagnosing without details or seeing it is mostly guess work)

The Wi-Fi is disabled either by you or the service has not started.
The drivers for your Wi-Fi adapter are missing, outdated or corrupt and need reinstalling.
The router is not pushing out a Wi-Fi signal so the laptop can't connect.

Start with the router it is the quickest. Then check the drivers and finally that the service for Wi-Fi has started.

If none of those help give some more details please and we will look into it.

My Lenovo G555 had 3 (yes, THREE) ways to turn off wireless. Slide switch on front edge, a function key (F4 + Fn?) and the software in Network Properties. All MUST BE ON! Check yours.