1) Right-click any network icon in the tray and choose Open Network Connections
2) Select the wireless adapter under LAN or High-Speed Internet
3) Click Change settings of this connection in the Network Tasks menu on the left
4) Click the Wireless Networks tab
5) Select your wireless network name from the list in the Preferred networks section
6) Click the Remove button
7) Click OK
Now you should be back in the Network Connections window.
Click View available wireless networks in the Network Tasks menu on the left.
Select your network from the list and choose Connect.
If it still doesn't show up, follow steps 1 through 4 again, then click the Advanced button... ensure you have one of the top 2 radio button options selected. i.e. NOT Computer-to-computer (ad hoc) networks only
The bottom box in Advanced should be UNchecked, for security, also.