Windows/Mac/Linux (All platforms with Java): Duplicate Files Searcher has a pretty modest name, but it's a powerful program for finding exact matches of files on one hard drive, across multiple systems, or on a CD or DVD compared to other storage systems. The Java-based, no-install-needed app simply has you add directories (and their sub-directories) to its list of places to search, including shared network files and removable discs. By default, the app will compare the hashed indexes of each file, and also do a byte-to-byte comparison of any potential matches found. You can also have it look for exact matches of name and date, and create pre-loaded databases of files to save time on future dupe-hunting sessions. It's also easy to switch the app's look and feel to match Linux, Mac, or Windows environments. Duplicate Files Searcher is a free download, requires a Java runtime environment to run. Thanks, jsong78!