I've always been intrigued on why MSN doesn't use Windows Media Player plug-ins. Well the reason is obvious is not upto par with the ubiquitous offering from Adobe - Flash. Check out all video properties on MSN - they use Flash!. But methinks that's about to change in the next few months. Silverlight is out and being used, albeit in beta form, on some properties. Check out http://sliverlight.net/fox
It's seems to be a good offering, Flash like menus and controls, and using VC-1 codec. So we are going to see good HD previews.