Total Commander - A Shareware file manager for Windows® 95/98/ME/NT/2000/XP/Vista/7, and Windows® 3.1.
VisiPics - VisiPics does more than just look for identical files, it goes beyond checksums to look for similar...
Double Commander - Double Commander is a cross-platform open source file manager with two panels side by side.
dupeGuru - dupeGuru is a tool for finding duplicate files on your computer.
XYplorer - File Manager for Windows
Pixiple - Find images similar in pixel and/or metadata content