Users of Windows Media Center just got a big boost in the variety of content available through their preferred media manager, as Microsoft announced on Wednesday that the Vista Home Premium and Ultimate users who are also Netflix unlimited members have access to over 12,000 movies and TV shows via WMC, effective immediately (give or take a couple of days).

The arrangement dramatically ups the appeal of WMC, especially for those users who don't feel the need to throw a TV tuner into their PC -- or, for that matter, to sign up for Netflix's Instantly To Your TV service.

The combination puts Netflix's excellent Watch Instantly collection directly into WMC's roster of available video, where it can be scrolled through and sorted like any other "aisle" of available video. Netflix members can also manage their DVD queues from within WMC.

Netflix's instant-watch videos are of course already available through the site itself, as long as you've got the correct (Silverlight) software installed, and the partnership between Microsoft and Netflix to bring Instant Watch to the Xbox 360 is nearly a year old now. There was even an extension available that melded certain Netflix and WMC functions -- written, as it happened, by a Netflix employee having some fun. Ben Reed, a senior product marketing manager for WMC, says that the value proposition here is the ease of discovery: Users love their online video viewing, but would prefer not to have to root around multiple sites to find the good stuff, not to mention having to learn a new set of controls for every player around.

The arrangement makes sense in light of recent efforts by Microsoft both to bulk up Media Center's offerings and to bring its TV, movie, and music thinking into closer accord. On the first front, we have the March launch of the Sports Channel, which combines news, video, stats and such from MSNBC.com, FOX Sports, CBSSports.com, and more for the major sports; the continued buildout of the MSNBC News portal is another good example of the direction in which Microsoft's thinking about content consumption.

More broadly, this move brings the company's "three screen" vision of viewing any content on your PC or your TV or your mobile device a bit closer to reality. And it's indicative that the push in-house at Microsoft to coordinate television, movie, and music efforts is serious business -- the Netflix-Microsoft partnerships already has quite a bit of history, in interesting contract to the comparative upheaval around other services such as Hulu.

The Netflix capabilities are rolling out, according to Microsoft, over the next 24-48 hours; at some point during that period, each machine that has run WMC in the past will gain a "Netflix" option under the TV + Movies section.