Instructions
Move your console closer to your wireless router if the Xbox 360 does not detect your network. You may be out of range, or there may be too many obstructions between the adapter and your router.
Check the power light on the adapter to make sure it is on. Sometimes power outages can cause issues with the adapter. Unplug it from the USB port, and then plug it back into the Xbox 360. A red light means the adapter is operational, and ready to connect to a wireless network. A green light means the adapter is connected to a network. A blinking red light indicates hardware failure.
Turn off other devices nearby that might cause interference in the signal between the adapter and the router. These include cordless phones, microwaves and other gaming devices.
Set your adapter to operate on the 802.11a signal by going into the "System Settings" of the Xbox 360, and change your wireless network to this same operation. The 802.11a operation tends to have less interference than 802.11b and 802.11g.