Check the firewall - turn it off to start with.
What is the DHCP server? Your ISP or another Computer?
What DHCP server program is running on it? (if you know)
Have you tried a static IP Address to see if that will work first? (if you can)
Can you ping 127.0.0.1 ? (localhost)
Does ifconfig show eth0? (Im guessing probably not but worth checking)
what does /etc/sysconfig/network-scripts/ifcfg-eth0 look like? (could be a configuration problem?)
These might help to resolve all this a bit more