What do you do in IIS if you get an error when trying to start your default web site and it says that it cannot be started because another web site may be using the same port?

For some reason I have IIS 6 and IIS 7 on the same machine. I seem to be unable to start IIS 7 but it seems I can in IIS 6. Yet, I am able to see c:\inetpub\wwwroot\iisstart.htm but I am not able to see a viable http://localhost