It would appear there is an issue with playback of DVDs stored on HDD. Here is the thread.
Question: does PDVD9.** not play *.mkvs out of the box? I have only ever used PDVD's codecs with a frontend, like MediaPortal or Zoomplayer. I have used .mkv as my preferred method of containing videos for over 5 years. Never realised this limitation of PDVD.
Another possible alternative to spending upgrade money could be to try ffdshow, as the later versions have full DXVA for HD media playback. Be aware, though, the app does tend to take over the system, & is not really for those after a player that just works.
I had a quick play with 10 and found there to be a problem playing mounted Blu-ray ISOs. Seemed like it was dropping frames. Yet if you opened the m2ts file directly from the mounted ISO it would play fine.