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I have an external hard drive, and I'm looking for a backup program to go with it to protect and transfer my files. I'm essentially trying to have an exact copy of one computer on multiple computers. I want the hard drive to be the one place with all my files, from multiple computers, that will automatically back up files and transfer files so both computers have them. So if I download a song to my music folder on one computer, the program would recognize it and back it up onto the external hard drive. And when i plug it in to the other computer the file would be copied to the same place. Does anyone know of a program like this? I would use programs like Dropbox or Amazon Cloud, But one of the computers is used somewhere without access to internet.