Been there
I have the same router (BEFSR41). Worked the same for me under 98se and XP.
Try the following:
1) Make sure all of the computers are set to "automatically detect network settings". Run "winipcfg" to release/renew IP addresses.
2) As Thrax said, go to 192.168.1.1 and make sure you have the right type of connection enabled. Go to the "Status" tab and do a DHCP Release, then Renew. It might not be a bad idea to unplug then replug the power to your modem first.
3) Though I have no logical explanation for it, sometimes when my power goes out all of my computers regain internet access automatically. At other times, I need to turn them all off, then bring them back online one at a time. You might try doing it that way. Once you get
one computer hitting the 'net through the router the rest should be easy.
4) Get rid of any of the Windows ICS stuff - your router doesn't need it, and Windows will just be confused (more than usual, that is...). Uninstall the stuff the "wizard cd" put on there. This is a "wizard" who
won't serve. (TWOO movie reference)
5) Make sure all of her computers are Folding! (Bet you already did that, though!

)
Sending you a pic of the router settings - make sure it's not one of those "local" IP addresses.