I got my brother a router, Linksys WRT54G.
The cable modem says Arris - Touchstone telephone

No matter what we do we can't have the router get an IP address from
Comcast.
We tried powering everything down for for ten minutes, connecting the
laptop directly to the internet (cable modem) and doing a ipconfig /release.
Also tried the MAC address cloning.
then we connected the cable modem to the router, powered up the cable
modem, waited two minutes, then powered up the router. We get an
internal IP via the wireless, but when we go to 192.168.1.1 -> status ip
address is still 0.0.0.0

What am I doing wrong?