Internet Problem!

Hi, I just got Comcast to install cable internet today, and my internet stopped working. Before, I had Qwest, and everything worked. Not sure if this has to do anything with it not working, just throwing it in there just in case. Otherwise, it keeps saying that it has "Limited or No Connectivity." When I tried to repair the problem, it keeps showing that it needs to renew the IP address, but it won't do it. What we've tried was: WinFix which many other forums said to try. I've tried to set up default IP's from what the provider has. I've reformatted the computer, installed the driver and still doesn't work. Is the network card broken?