When setting up a streaming media server, especially in applications where you will be using "push" to connect to the server you invariably have to run this service on port 80.  This becomes a problem immediately if you want to run another service on the same server that uses port 80, like..well IIS and all web http services.

If you intend to broadcast over the Internet you at that point need a separate server for streaming media.  You could run your web services on another port; although the search engines and some browsers look at this a security issue.  You can do some trickery and run your media services on Port 80-84 which could fool some media players some of the time, but won't fool all of the firewalls every time.

Check your router and firewall settings carefully for your first broadcast.  You want to open all affected ports (or leave the streaming server in DMZ with a firewall) and configure port-forwarding for windows media services if using a standard router with mulitple local IP's.

When streaming over the internet you could configure the http server control protocol. You have to specify this properties in the server configuration, and can choose another port than 80 if you want, but see cautions above...