Looks like Microsoft has teamed up with the MLB for the promotion of its Silverlight media player.
Now when you go to MLB team sites to watch video clips and highlights, you'll be encouraged to get a copy of Silverlight browser plug-in media player. This type of deal is beneficial for the MLB, which will want to protect its content, and for Silverlight, as Microsoft is looking to push it out through existing companies. Silverlight can be used as a good media player for its support of DRM-encrypted content.
The Silverlight plug-in only works with Windows XP, Vista and Server 2003 with Internet Explorer 7. Previous versions of IE are not supported, nor are Firefox, or Windows 2000. You can also use Silverlight on Macs, but the Linux OS is not supported either.