When you run the NAV 2013 RTM installer and want to install the demo-database on an already existing SQL-server (for instance your own local developer-edition-server), the installer requires that TCP/IP is enabled on that SQL-server.
(see
http://msdn.microsoft.com/en-us/library/bb909712%28v=vs.90%29.aspx for instructions on how to enable it)
The NST-server does not seem to have this requirement, it looks like it's only the installer that requires this.