Doppelganger

From Salty Brine Software:

Doppelganger is a powerful and reliable tool to find and remove duplicate pictures, documents, music files, and more! Removing duplicates frees up disk space and aids your computer in indexing. If you backup your files, removing duplicates first reduces the storage space required for the backups and the amount of time required to perform the backup. Most people are not aware of how many duplicate files reside on their computer and how much space these duplicate files are taking up. Doppelganger locates the duplicate files on your computer. It can find matching files even if their names are different! Once found, Doppelganger can also help you safely remove these duplicates. Doppelganger is based on the duplicate file finder functionality in our software FolderMatch. As such, it has over a decade of Windows file system knowledge and experience behind it. Its core programming code has been tested and refined by the feedback of millions of users. It's rock solid and you can trust your data to it. It's also FAST! In all of our testing of comparable software, it's one of the fastest we've found. Search for duplicates based on file name, size, date/times, and/or contents. Specific files and folders can be excluded from the search. Once found, the duplicate files can be treated in several ways: they can be moved to another folder, or sent to the Windows Recycle Bin, or they can be deleted permanently.