are you talking about DHCP here? have you tried using a static ip if you are hooked up to a router? got link lights on the nic? check to see if somehow the nic got disabled in bios(not likely)
you might want to try pinging the other pc's on the lan. if you try another network card and all else fails as well there IS a registry trick which i had to do which worked. the path is in
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControSet\Service s\Winsock
heres the thread with the
answer that worked for me. id only use it if everything else fails like it did for me.