I recently upgraded from Visual Studio 2010 to the Visual Studio 2012 RC. The installer also installs IIS 8 Express which Visual Studio now uses as the default web server.>
I am not sure if you have edited right configuration file. Try following steps
open %userprofile%\ducuments\iisexpress\config\applicationhost.config
By default bellow given entries are commented in the applicationhost.config file. uncomment these entries.