Windows Media Player isn't working on some DVDs?
So I have Windows Media Player, but I don't know which generation it is. I expect it's quite up to date since I have Windows 7 Ultimate. Anyway, I tried to watch a DVD on it, but the screen's black, however, the name of the film and then the cast pops up in the left hand corner, as if it's kind of working, but nothing is happening. I then tried to watch another DVD and it worked, but this one, and another didn't. They're both perfect condition, I promise. What should I do?