Yes, I did try diagnostics: Everything's fine per Win7.
Development: We disabled the on board adapter and installed a USB adapter, which saw our network and connected. I used the "Home" profile for it and confirmed the Firewall setting, then went on to reconnect to my desktop's Home Group (success).
I then disabled the USB and enabled the on board adapter, which didn't see any connections again. It also still retained the "Public" Firewall profile. Which is unchangeable in that I can't connect to a network with it -the only status under which one can change the "Location" or Firewall "profile".
Theory: I may be nuts, but I say the on board adapter will only connect to the friend's network as that's the only "Public" network it will see now (bug?), but once connected it will give my son the chance to change it's profile back to "Home" so it'll see all available networks like the USB does. He's on his way to try. More later.