To fix these errors, try:
The system will scan all drives for Windows installations. It will say: "Total identified Windows installations: 1" . When asked "Add installation to boot list? (Yes/No/All)" – type Y and press Enter.
You do not need a product key to repair an existing installation. Microsoft provides a tool to download a legitimate ISO.
If you are unable to download Bootmgr or if the above steps do not resolve the issue, there are alternative methods to fix Bootmgr problems:
The MBR locates the active partition and loads its VBR.
If you are seeing this dreaded black screen, your day is about to get stressful. The Windows Boot Manager (BOOTMGR) is a critical system file that tells your computer how to start Windows 7. When it goes missing or becomes corrupted, your PC becomes an expensive paperweight.
