Re: System State Backup for Windows 2003/2008/2012
The ntbackup .bkf file will only be created during Windows Server 2003 legacy system state backups. The VSS System State plug-in should be used on newer versions of Windows.
If you need to remove the .bkf file after a successful backup, I'd recommend using a post-script to remove it. You can find more information on configuring post-scripts in the EMC Avamar 6.1 for Windows Server User Guide. In REV 03 of the document, this information can be found on page 180.