Don't download anything. I had the same problem and scratched my head numerous times until I saw a tip on another forum. Put all the annoying MP4 files (video clips etc) into one folder and put on desktop. Remember the folder name. Turn off your computer. Restart your computer and as soon as your desktop shows (even without the computer being fully boosted) right click on the named folder (egg timer might show for a few seconds) and click delete. This should go straight to your recycle bin - you have to be faster than the computer - and then delete from recycle bin. You should feel a magic moment when it works.