iMac wont connect to internet

OK.. I hope someone has an answer to this...

I HAD a custom built PowerMac G4 Sawtooth that was a faithful machine. Rarely had any problems with it. I have CABLE INTERNET. The G4 connected to the internet FINE via Ethernet. I recently bought an iMac Intel Core Duo from a friend and proceeded to use the migration assistant to move my files over.

The iMac now serving as the main machine WILL NOT connect to the internet via the SAME ethernet cable and modem setup that the G4 had ZERO problems with. Fortunately my neighbor has wifi and im able to use his.

I just dont get it though, WHY WHY WHY will the iMac not connect? It says its connected to the modem but the internet just fails. Ive tried power cycling so i know that wont work. This is DCHP, it should just work.... ?

To make matters worse, during the transfer from the G4 i forgot to eject the system properly and shut it down while in TDM. So shes dead... Wont power on at all.

So i have no other system with which to check the internet connection on. This is the first time ive ever had something like this happen.. Im actually frustrated with my MAC. :-/

HELP!