Is there a wireless icon on one of your Function keys? Try tapping that with and without holding down the Fn key to the left of your spacebar.
If that also fails, look in Control Panel>Device Manager and expand the Network Adapters entry.
The wireless device should show up so right click it and go to Properties. Check it's Enabled and also look in Power Management and remove the tick from "Allow the computer to turn this device off". Apply and OK your way out, restart the computer and try to connect to the Net again.