Tom…there’s more to your question. I think the only way to find duplicates is by file name, or just by looking at the thumbnails.
Image Viewers will not have that feature. You need something that just looks at your file names.

I have used CCleaner and Glary Utitlities. In Glary Utitlities you go to the Cleanup and Repair module and then choose the Disk Cleaner module. This will scan your entire hard drive and find all the duplicate file names and then present them to you for deletion. You can then delete all the duplicates or just go through them and choose the ones to delete.

Let me know if this works.