Right-click on any file in your Downloads window & choose 'Locate File on Disk' from the menu; http://www.gnutellaforums.com/gettin...disk-tool.html which should take you to the incomplete folder. Check if the missing files are inside there.

Search the title of the missing video(s) on your computer, see if it shows anywhere. You could also search .avi or .mpg or whatever file extension it had.