ERROR - Windows Server Backup has detected that the selected backup destination %1 contains backups taken with a previous ...

ERROR - Windows Server Backup has detected that the selected backup 
destination %1 contains backups taken with a previous version of Windows. 
Performing a new backup to the destination will cause previous backups 
to get erased. Copy the existing backups to a different location and rerun 
the backup job with -allowDeleteOldBackups for the new backup to succeed.