Here's an interesting bit of news. CNET Australia has reported that the version of Windows Media Player included with Windows Vista will not play back Blu-ray nor HD DVD movies.
The version of Windows Media Player that will ship with Windows Vista won't include playback support for either Blu-ray or HD DVD movie titles.
"In box we have the Microsoft VC1 decoder...but in order to do playback [of Blu-ray and HD DVD titles] you will need a third-party player such as...PowerDVD from Cyberlink," Mark O'Shea, OEM Systems Engineer for Microsoft Australia told CNET.com.au.
VC-1 is a Microsoft-developed video codec adopted by many movie studios as the video standard for their commercial HD DVD and Blu-ray titles.
I can't say I'm surprised. The current version of Windows Media Player doesn't play back standard DVD movies without drivers from a 3rd party either. If you'd like to read more, the entire article can be found here.