The print screen button doesn't work with a lot
of movie/dvd players, all you get is sort of a
clear window. I've found that you need a
capturing program designed for taking a shot of
that kind of screen.
I use PowerDVD to play my dvds and it has an
easy screencapture feature. It takes it in the
wrong ratio though (too wide), and I haven't
figured out how to fix that yet, so I just
adjust that in Paint Shop Pro.