One of windows default settings can wreak havoc on wireless connections. It wants to automatically log on to a domain server, which will prevent or disable the wireless cards settings. Most home networks do not need, want, nor use a domain server. Try going into the network properties, click on microsoft client for networks, click properties, and disable the "feature". While in network properties, check to see if the cards settings match those of the router (channel, SSID, encryption, etc.). You will probably need to reboot after changing any settings.