NTBackup (Microsoft Windows NT backup)

NTBackup is a built-in backup application introduced with Microsoft Windows NT. 

NTBackup was designed to allow small and mid-sized organizations back up their servers without requiring third-party backup software. NTBackup becomes less reliable as the volume of data increases. It's possible for administrators to complete a multi-gigabit backup, but they may receive an error message during a restore.

NTBackup files have a .BKF file extension. When Microsoft created Windows Vista and Windows Server 2008, they retired NTBackup and created a new backup utility called Windows Server Backup. Windows Server Backup can't restore .BKF files created by NTBackup, so Microsoft created the Windows NT Backup - Restore Utility that will allow .BKF files to be restored to machines running newer versions of Windows.