Problems

I just installed redhat linux 7.0 two nights ago and i cant for the life of me get the networking right to connect to NTL broadband. The network card works fine and is recognised by linux and i can asign myself an IP address but whenever i try enabling DHCP it wont work. Even if i enter all the IP, DNS, Gatewat etc it still acts like it isnt on the NTL network. Do i need to change any of the .conf files or host files? If anyone could help me i would be very grateful or point me in the direction of a good web based guide
-Adam