Turn on easy backup of personal files.
By activating the File History function, your files in your personal file directories (Documents, Desktop, Music, Pictures, Videos) will automatically be backed up.
To access the File History tool, go to Settings in the Charms bar, Change PC settings, Update and recovery, and File History. The first time you connect an external storage drive, all the files in your personal file directories will be copied to it and placed under a directory named File History. Any changes made to these files (such as being deleted, renamed, or updated) will be mirrored to this external drive when it’s connected to your Windows 8.1 device.