chkdsk C: /f /r
From Windows PE command prompt:
fdisk /dev/sda # Use 'a' to toggle active flag on the correct partition active partition recovery full
diskpart select disk 0 select partition 1 active exit After restoring structure, check for file system corruption: chkdsk C: /f /r From Windows PE command
# Mount root partition mount /dev/sda1 /mnt # Reinstall GRUB grub-install --root-directory=/mnt /dev/sda update-grub Using fdisk (Linux): active partition recovery full