Validating identity wireless router
When I put the CD in the computer, and after getting the Starting installation wizard message, a software setup screen then comes up with Select components.2 boxes with check marks on them. I told her that if we don't get this darn thing resolved before Sunday night, I'll just return it to Comcast and try another one. If the modem and the computer are within reasonable proximity, connect them with an ethernet cable.
First box says Hardware enabling driver, second box says Software applications. I was happy to see that, when I accessed her wireless network, instead of almost instantly getting the [endless] certificate/Validating routine, I got that familiar opening of the box (Wireless Network Connection) with Type the key, and then click Connect. Disable the computer's wifi adapter and enable the ethernet port and reboot the computer. On the left side you will see "Change order of preferred networks" click on it.
One way to restore networking, especially wireless, is to go into control panel, system and delete the network card. Since you mentioned that this notebook had previously been setup for multiple wireless profiles, my suggestion would be to delete all existing wireless profiles and see if that allows you to then create a new profile for the Comcast gateway.
I can't provide a screen shot to illustrate how to do that because I don't know if you are using the built-in Windows Wireless Zero Config, or a vendor specific utility for your unnamed Wi Fi card.
Manually configure a static ip address for the wireless network to see whether it can access the internet.