dupeGuru is a multi-platform ready tool. It works perfectly not only on Windows platform, from XP to Windows 7, but also on both Linux and Mac OS X. It’s an open source application but not free. The folks at Hardcoded Software who built the tool calls it fairware, open source software developed with expectation of fair contributions from users. If you don’t buy a license which is $19.95US, you are still able to use the tool to find all the duplications but are limited only able to remove/copy 10 duplicates at once.