If you mean the lossless stuff it currently plays dolby true-HD and PCM, but not DTS-HD MA yet
Even though it downmixes soundtracks to 48k this is still considered lossless/high def. The majority of soundtracks only come at 48k anyway and to be honest i bet most people haven't got the kit to tell the difference anyway.
Some people claim that the latest build of PowerDVD doesn't downmix high rate soundtracks, others aren't sure, and even more don't own a 96k track at all. To me it seems that most can't tell the difference. I certainly can't. Maybe I need to replace my 3 grand system or my ears

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What I do know is that my favourite soundtrack is Transformers and thats not even lossless