Hi Woodelf.
I saw this thread when you first posted but I didn't reply because I wasn't sure that I could help. I'm still not but Sunny-Dave has posted in Chatterbank, asking me to take a look at your question, so I'll provide what little information I can.
DVDs of movies and TV programmes have only ever been produced with the intention that they're played on 'proper' DVD players (rather than on computers). However the overlap of technologies has meant that DVDs can (theoretically at least) be viewed on PCs. That's caused problems for the companies that produce the DVDs because anything that can be played by a computer can also be copied by the same computer, leading to the illegal copying (and potential sale) of DVDs.
So, for a while at least, there was a big surge in the production of DVDs incorporating 'DRM' ( = 'digital rights management'), which was specifically intended to ensure that they couldn't be played on computers. However that caused an outcry from people who found that they couldn't view movies on their computers, so DRM is far less common that it used to be.
So it's possible that you've got some DVDs issued with DRM, and some without it.
A different media player, such as the excellent VLC that Sunny-Dave recommended, might help but I can't be sure of it. Also, as suggested, getting hold of the latest driver for your video card might possibly offer a solution.
Regrettably, however, I can't think of a way of explaining to someone with a visual handicap (using a screen reader) how to accomplish those tasks. I hope that you know of someone who is 'computer-savvy' who can take a look at my reply and try the suggestions offered here for you.