Most DVD playback software uses DirectX to 
display the image on the screen. That's the 
little rectangle with the image. 

DirectX bypasses most of the usual Windows 
operating system to improve performance. The side 
effect is that normal Windows functions 
can't "see" DirectX images. Hence, the little 
black rectangle when you try to capture it. 

So where does that leave you? If you want to get 
a screen cap, you'll need to use your DVD 
software's screen capture function to do it. Some 
have it, some don't. 

I use WinDVD. The more recent versions let you 
capture what's showing into a file by hitting 
the "P" key. You can download WinDVD at 
Intervideo (www.intervideo.com) for a free trial. 

When you get WinDVD, try hitting P key while the 
video is playing and look for a .bmp file in the 
capture directory under which WinDVD was 
installed. 

Good luck!
Chi