Actually, MS has warned us that Win 10 TP will not play DVDs on Windows Media Player.
There is a section on Important notes:
(excerpt ) After you install the preview, you won't be able to play DVDs using Windows Media Player.
One will have to click a few links before one can see the warnings.
But that's besides the point.
Now I am updating my question......
If it is so easy for the Win 10 system to accept VLC, a 3rd party application, why is it so hard to accept Windows Media Player which is a MS product ?