Capture still images from Windows Media Player Screen -Amit Agarwal

Why you cannot capture?
When the video plays, it is actually displayed on a different surface/layer called overlay that is produced by hardware acceleration. When you take a normal screen capture, you're taking it of the normal surface where the video isn't displayed. That's why it comes out black as it is invisible to the screen capture software.

Solutions:
1. In WMP, at least since version 9, you can use Ctrl-I to capture a frame, either when playing or when paused for greater accuracy. It brings up a Save Captured Image dialog which handily defaults to a jpeg. This works only if the video you are watching is using a Microsoft supported movie file.

2. Turning off hardware acceleration in the application that is playing the video, or disable hardware acceleration system wide.

3. Or simply use another media player such as Power DVD, WinDVD or BSPlayer which can take screenshots or use a screen-capture software.