bootrec /fixboot — Writes a new boot sector to the partition.
If your computer refuses to boot or displays errors like "Operating System not found," a damaged Master Boot Record (MBR) is often the culprit. You can fix this using built-in Windows tools or dedicated third-party software. Hard Drive Mbr Repair Software
: Select Repair your computer > Troubleshoot > Advanced options > Command Prompt . bootrec /fixboot — Writes a new boot sector