Re: Using pc as media server.
Provided the main PC is running a fairly recent version of Windows you can set up shares on this machine to the media you want to stream and then set up Media Center on client PCs to include these shares in the Library. As for the Xbox, you can set this up as a Media Center Extension device (you'll have to google that one).
But I'm trying, Ringo. I'm trying real hard... to be the Shepherd.