What is DupDetector?
Dup Detector finds duplicate and near duplicate images by opening and reading image pixel data. The program is easy to use, just specify the path and start the scan. You can specify a match % that is required to consider the image a duplicate and preview all found dups side by side with an option to delete either one. Supports 10 image file formats (jpg, gif, bmp, png, tif, pcx, tga, wmf, emf, psp).
The official website is no longer available. Last version, 3.3.02, released in August 2011, can be still downloaded from Wayback Machine
Comments and Reviews
Said about DupDetector as an alternative
Other options are finding EXACT duplicates. Visipics and DupDetector finds SIMILAR images regardless of their condition. Other suggestions mostly can NOT do that.