I initially started with an 80 GB folder, and the program crashed on me midway through. 2nd time the same result. I then read the instructions, which urge you to go no higher than 20GB and to start out with short playlists (with dupes on it?). Its probably OK for the price and for smaller collections. Unlike Liten it uses time length in its criteria, which is needed for accurate matching. But its not for my purposes. For larger folders not on your computer, try Gemini. For more cautious deduping of files on an external drive, Araxis is a good choice. In fact, for about ten bucks both Gemini and Araxis can be purchased. They complement one another. For sophisticated refining of a computer folder (i.e. iTunes), try TuneUp. The CEO is invovlved, supportive, and conscientious, despite some of the bad reviews suggesting otherwise.