Hey JL, registered just so I could answer you.
For deleting duplicates of ANY kind, I use the Search function in Total Commander. On the second pane of the Search function, you can choose to look for duplicates by name, size and contents. You can also search subdirectories, I think it even does so by default. It will then display its search results paired and separated by dotted lines so that you can quickview them and delete the duplicate you do not want. Total Commander is Shareware with a nag box, otherwise fully functional, and is - in my opinion - the most useful and versatile program for Windows that has ever been.
http://www.ghisler.com/
The most advanced tool for the job would be IMGSeek, which has its entire browsing experience setup around the idea of visual similarities between images. Double-clicking on an image in that program will display photos that look like that photo. However, IMGSeek has a very hard time (crashes) handling image files that are not completely adherent to standards, damaged files and the like. And when it crashes, you lose what you were doing. IMGSeek is also not a very user-friendly program. IMGSeek is GPL or somesuch, free for noncommercial use.
http://www.imgseek.net/
I beleive XNView incorporates a similar function now in Tools->Find Similar Files, and select "Similar picture content (slow)". Try the slider, don't leave it on 95%+ unless you are looking for actual duplicate files, exactly alike. XNView is freeware for noncommercial use.
http://www.xnview.com/
And to think I came here originally to find out whether Microsoft's SyncToy 2.1 could be used to sync A with B and then B with C, or if that would mess things up. I'll just keep looking, but I hope the info above helps someone.
/ Per
