There is a GUI option for Robocopy, though the CLI works just fine as well. For more information on the GUI, review the following article: Utility Spotlight.
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there is a program I believe is called Robocopy. it will move the data to another place and also keep the security that was on it in place. then just change the AD account to point to the new directory. yes it has to be done when they are not logged in or they will start receiving a lot of errors and the copy will not work correctly because of open files.