How do I find a wireless network that is not on the list of available networks?
If you have connected to the network before, make sure your computer is in range of the network (no more than 150 feet indoors and 300 feet outdoors for 802.11b and 802.11g hardware and no more than 50 feet indoors and 100 feet outdoors for 802.11a hardware), the router or access point is turned on (if you have access to the router or access point), and the wireless switch on your computer is turned on. (Not all computers have a switch; if yours does, it is typically located on the front or side of the computer.) If you have not connected to the network, broadcasting might be turned off and you might have to manually add the network. To add a network that is not broadcasting, follow these steps:
Note: This information provided by Microsoft.