I am considerting getting a Blu-ray drive for my PC. If I get the Blu-ray drive for my PC, can I use the media extender features of Xbox 360/Vista to play that disc on my TV?
I don't think so.
You won't be able to do that with HD DVD or regular DVDs either. I believe anything carrying copy protection can't be streamed.
Also, the 360 as an extender is very limited in terms of audio format support. Therefore, even having ripped the movie to the HD
(and removing AACS in the process) won't solve your problem.
************************************** What types of media stored on my Windows Vista-based PC can I access through my Xbox 360
Live and recorded TV, digital photos, digital music, home video, and exclusive online multimedia content, such as news clips, downloadable music, local weather, RSS feeds, and more.
Video formats
MPEG-1 with MPEG audio
MPEG-2 with MPEG audio or AC-3 audio
WMV 7, 8, and 9 with WMA Standard or WMA Pro audio
Yeah, as far as I'm aware you can't play anything from a disc drive to an extender. The content has to be on the hard drive and as Diogen said, is quite limited.