I want to empty these downloaded movies from itunes

When I download my personal .mp4 files into itunes, it puts them in this area under Settings Movies. I have to click them on or off to get them to sync to my phone. When I move the original .mp4 file and reload it to itunes, it makes another copy in here. I just want to empty this area and start over, but can't find any place to do so. Help! I just want this area clean for a fresh start -- there are now hundreds of repeated movies in here! Thanks --rt.