In Windows Vista, Windows 7, Windows 8, Windows 8.1, or Windows 10, the “BOOTMGR is Missing” boot problem can be fixed.
BOOTMGR error messages that aren’t BOOTMGR:
“BOOTMGR is missing” is the most probable error message to appear. “To restart, press Ctrl+Alt+Del,” however, your PC may also say, “Couldn’t detect BOOTMGR.”
These terms allude to the same problem that is preventing your computer from booting up.