: Select Repair your computer > Troubleshoot > Advanced options > Command Prompt .
bootrec /fixboot — Writes a new boot sector to the partition. Hard Drive Mbr Repair Software
: Type these commands in order, pressing Enter after each: : Select Repair your computer > Troubleshoot >
This is the most direct method and doesn't require downloading extra software if you have a Windows installation or recovery USB. Hard Drive Mbr Repair Software