Well this is caused by a few things
1. There are no wireless networks in range. This is not likely unless you live more than 300 feet from anyone else, and don't have a wireless connection yourself.
2. Your WiFi card is shut off, check your manual and see if your laptop has a switch of button combination to turn it back on.
3. Your WiFi software has a feature to shut off the wireless card outside of a physical button, check that.
4. Your drivers are messed up, go to the vendor support page, download and re-install the drivers.