BOOTMGR Missing on BMR of Windows
Make sure you boot from the default O.S. installation media / ISO / CD-DVD / once booted up make sure you try to follow the detailed steps below:
If this happens login via console to run the following:
cdboot D:\windows
BOOTREC /FIXMBR
BOOTREC /FIXBOOT
BOOTREC /REBUILDBCD
BOOTREC /SCANOS
***NOTE: Replace D:\ with the drive letter where the system is installed. Basically switch to partition where windows files are located/restored and run those commands.