Emptying trash can of an MP4 file
I have a mysterious MP4 file that I cannot get rid of, apparently because it is constantly and persistently in use, though what it is doing eludes me. The name of the file is p02cyg5.mp4, but I suspect that means nothing. Double clicking on the file starts a long conversion process producing a white window with a time bar and a play/pause button Starting the file produces no picture and no sound. The time bar indicates a total of 57 minutes. (I would upload an image of the file's info, but the Apple equivalent of Windows' quite easy to use PrntScrn function seems to be problematic.)
MacBook Air, OS X Yosemite (10.10.2)