Windows 7 comes with a built-in tool which assists a user to back-up his or her data and settings to another computer. Easy Transfer will save all data on a hard drive to a .mig migration file, that can then be accessed on a new Windows computer. Encryption is available for the file. Unfortunately Easy Transfer is not available on the Windows 10 operating system, which uses PC Mover instead.
The .mig file condenses a PC's data. Be sure to look for such files when conducting a forensic review of a computer. They can be valuable archives of a user's data from a particular point in time.