I appreciate the reply! I still must think the problem has something to do with the Windows 7 installation, since the problem began immediately upon the installation. Also, as I said, we already downloaded the drivers. Plus, regarding the wireless card, he gets connectivity if he moves the laptop closer to the wireless modem next to my desktop, within range of it. So the problem must lie with the extender.
My son still hasn't tried the fix mentioned in the first reply, but as soon as he does, I'll report. Thanks to all, meanwhile!