Giddy-up partner, Visual Search Pony is riding to the rescue. Rescuing your hard drive space that is. This handy free utility identifies duplicate video files so you can free up space by helping them git along to the Recycle Bin. Better yet, it identifies them even if the if the format, name, or resolution are different--the program uses other criteria--so it finds copies that other duplicate finders miss.
Visual Search Pony's interface is simplicity itself: a preview pane, search pane for adding locations to search, and a pane that lists the results of your search. I keep a folder of video files which contains the same videos in a number of different formats for testing the players I review. Dag gum it if VSP didn't up and find all my diversely-named AVI, WMV, DivX and MP4 files and list them as duplicates.
Unfortunately, VSP doesn't understand OGG Theora or Quicktime though it also handles SWF, MKV, and FLV with the proper DirectShow codecs installed. There could be a bit more information on the VisualSearchPony.com Web site about where to find the codecs, but that's not the program's real job. Only five years ago duplicate videos wouldn't have been a problem. Today, with uploading and downloading video from cameras, recorders, flash drives and the Internet as common as brushing your teeth, it most certainly can be. Visual Search Pony is great tool for culling the herd. I wish it supported Ogg Theora and Quicktime, etc. but it's handy enough as is.