How can I stream live TV from Windows Media Center to another computer?

See this article : "Streaming Live TV" , for how to do that using VideoLAN.

"You could try Mediaportal. It works really well, is completely free, and open source.

Add guide data from a variety of sources like DVB signal, web (via
XMLTV) or Clickfinder (Germany)
Define as many channel groups as you wish, such as Favorites, News,
Sports, Music, Movies
Change channel groups
Search programs by name, genre or channel
View all upcoming airings of your favorite shows
Select the IMDB (Internet Movie Database) option for more movie
details and images

If you have more than one PC in your home, you no longer have to
install a TV card into every one. Simply place your TV card(s) in one
PC and install MediaPortal with the ""Dedicated TV server"" option.
Then, on all your other PCs install the ""MediaPortal client"" option to
receive live, or recorded TV, and TV guide data from your server."