“Tearing” of screen image on the secondary monitor of a cloned set while playing a movie
You have a computer which supports two monitors and have them configured for “clone” mode, and you do not have the display configured to use Windows Aero. When playing a DVD movie, an artifact called “tearing” may appear on the secondary monitor. Tearing is a video artifact in which the top portion of the screen shows a different frame of video than the bottom portion. During scenes containing fast motion, there may be a noticeable horizontal line at the point where the two frames meet.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB972195.