during my travels i found a duplicate image detector absolutely free here=
Photo-Freeware.net - DupDetector Download
hope this is helpful to some, but after a crash may not help, i should explain-
up until now i have been using a program called ''no-clone'' which is good software and will search the whole computer for duplicate files, great, as long as those files are the same size or dimensions, my problem arose because of an external drive crashing and after recovering many files they are no longer listed as the same size or dimensions in their properties, i can see with the naked eye that some are exactly the same but programs like ''no-clone'' and the one above will not detect them and i needed one that did....
i have found one that scans for identical images regardless of the file size or dimensions called ''Visual Similarity Duplicate Image Finder'', it works, costs around £20 but a free trial can be got here=
//visual-similarity-duplicate-image-finder.mindgems-inc.qarchive.org/
Magoo.