currently, there's NO (at least simple) way to just rip a HD movie itself. the above mentioned from thegreek is to rip regular DVD movies.
@ thegreek, could you verify DVDShrink could just rip the main movie (I know it could) and the 5.1DD sound track (that I'm not quite sure!!)??? if you hook up to your receiver (I assume you do from you HTPC), will the receiver showing it's getting DD/DTS steam?? reason I ask is I've yet to find a software that could just rip the main movie and retain the 5.1DD audio track.....
I am not positive if it can do it with the free version or not, I am not even sure with the version you have to buy. But have you tried dvd fab HDdecrypter?