I blogged about this a couple of weeks ago. MSNBC and news.com had articles back on 1/18 about it.
Here is the deal. Buy Vista Ultimate. Then get up to two copies of Home Premium for $49.99 each.
here is where you get exact information on how to get this program. www.windowsvista.com/familyoffer
I couldn't find this anywhere, people were coming into Best buy asking about it. It was very hard to find it anywhere on Microsoft Websites.
So go to the site, it explains exactly how to get it. If you really think about it less that $500 for Vista on three PC's. They can all run Media center.
here is a blog entry about it.