I have a fedora core machine, and it is picking up an IPV6 address, but not an IPV4 address. I have done
dhclient -r eth0 but the ipv4 address has not come. I have reset the port using
ifconfig, but the address keeps coming up as an IPV6 address.
It's possible that the lightning strike destroyed the network port on your machine, and that the IPv6 address is a self-assigned address. Have you tried using the 'ping6' command to try pinging an outside IP address via IPv6 to really ensure that you've got IPv6 connectivity to the outside world?
Also, I concur with mattdm here -- FC4 is very old -- it's definitely worth looking to upgrade to a more modern version of Fedora.
It might be that you are looking at the wrong end of the cable, i.e., the router's DHCP server went AWOL for some reason (board/network card fried, configuration scrambled, cable is shot, ...).
As comments indicate, Fedora Core 4 is from the Jurassic, by now your average sieve has less known holes. You might want to look into some very-low-resource distribution, or upgrade both the machine and the distribution.