Boot Manager Repair Software -
If built-in tools fail, these third-party options offer "one-click" fixes or specialized recovery environments.
A powerful command-line utility used to update or rebuild the MBR and boot sector. bootrec /fixmbr : Repairs the Master Boot Record. Boot Manager Repair Software
A free, community-driven emergency boot disk based on Windows PE that includes various MBR and partition repair tools. If built-in tools fail, these third-party options offer
Microsoft provides native tools to fix a corrupted Boot Configuration Data (BCD) file or Master Boot Record (MBR). If built-in tools fail
Which operating system and version are you trying to repair? Windows startup issues troubleshooting - Microsoft Learn
Ved Puran