I've used System Mechanic for years. It's about the best tools out there.
One of it's applications will delete duplicate files, as stated. This process can be detrimental to your computers health. Be very careful as to what files you remove. I had over 600 duplicate files and over half of them needed to be left alone. Many programs have the same files and therefore you'll see multiple dups. Deleting the wrong ones can cause a mess.
Be careful.
brad