Screen captures of movie players, such as Windows Media Player,
sometimes turn out blank because the movie is projected onto what is called a hardware overlay surface.
Capturing this surface results in a blank spot that's usually black, but can be any color.
The solution is to tell the player not to use hardware overlay during the recording by turning off "hardware acceleration".
For how to do that, choose DVD or Other below:
DVDs - DVDs, even home made ones, sometimes require special procedures