The Special menu lets you preview video files so that you can quickly browse and find movies on your computer. You can play QuickTime, MPEG 4, AVI, DV movies, and any other video file that can be opened by QuickTime.
Open the Application Wizard pane in System Preferences and click Menus.
Click the Customize Menus button. In the dialog that appears, click Special.
Click the Customize Previews button. In the Previews panel:
Deselect the "Play movies" checkbox if you do not want the Special menu to preview movies. Alternatively, you can disable previews for specific types of video files.
Deselect the "Frame previews" checkbox if you do not want to display movies in a frame.
Drag the Movies slider to adjust the size of video file previews.
If the Special menu does not play movies despite the "Play movies" checkbox in the Previews panel is selected, you may have disabled previews. To re-enable them, click the Customize Menus button in the Menus pane of the Application Wizard preferences, click Special, and select the "Show previews" checkbox.