So, Slightly confused, The Wifi adapter is not picking up the Network as in it isn't connecting to wifi or are you meaning it is connected but not working? Or the common thing of just only your Desktop cannot seem to pick up any networks while others can? I think I understand what your saying, I encountered similar like problems as a Computer tech in school, However yours doesn't seem to pick up any networks at all?
Everything plugged in right? Updated or is there outdated software? I'd probably be able to understand it better if I saw the problem first hand,
What I'd recommend doing is seeing if there is a way to troubleshoot the problem, And if so make sure the WI-FI AP Channel is supported by the machines client. Also make sure the adapter is set to broadcast it's SSID, Make sure WMM (qos) is enabled. And if your using a wireless network make sure it is set to WPA2 (AES-CCMP). If none of these work I would recommend getting a technician to take a look at it because past that I'm not sure what would be the problem.