Taking a scrfeenshot of a .avi video file

So I want to take a screenshot of a .avi file, but whenever I do the video image just turns into a black screen.  Can anyone help me out here?

>>11
Yeah, but I believe >>8 meant there's something like Print Screen in the iOperatingSystem, yet it's disabled while you play iVideos in some iPlayer; Apple can shove that iRights iManagement iShit up their iAsses.