You need the vmcNetFlix plugin. It's compatible with  Microsoft Windows Vista Media Center.It can do a lot:-

• Stream WatchNow movies directly to the Media Center player.
• Download WatchNow movies to a "Watch Later" gallery.
• Support for Vista Extenders on both x86 and x64 platforms.
• Support for NetFilx Instant Queue.
• Support for Episode listings.
• Search for movies by keyword.
• Browse DVD and WatchNow movies by genres.
• Sort Gallery by Title or Year.
• View your queue, history, and recommendations.
• Add, remove, move movies in your queue.
• Supports DVD/Movie Partental Controls
• Dynamically switch between small, medium and large gallery listings using FastForward and Rewind buttons on your remote.
• Switch to full screen anytime video is playing by simply pressing the Play button on your remote.
• Prevents standby/sleep while downloads are still in the queue - requires Vista Media Center PC to be configured in "Away Mode".

Now, to get your Movie Now stream working on more than three media centers, all you need to do is copy the working registry entry from one machine to another. The key you need to copy is HKEY_CURRENT_USER\Software\Netflix\Movie Viewer.

Check it here how to:-

http://www.ehomeupgrade.com/2008/05/27/watch-netflixs-watch-now-on-unlimited-machines/