I would first check that wireless is switched on -- most laptops have a physical switch on the side or front of the case usually with an indicator LED.
Then go to Windows Control Panel, System, Hardware, Device Manager and see if the wireless network adapter is present or whether it is Yellow Flagged as faulty. You may need to delete the device and re-install it -- perhaps take the opportunity to download a more recent driver set from the laptop or adapter manufacturer's website.
Obviously also check Windows Network Connections etc.