1. Grub Boot Loader Windows 10

Upgrade Windows from 7 - 10. During installation process, after the first reboot, i get the grub rescue prompt, fixed this with BootRepair in a USB stick. Grub now appears, but is only showing Ubuntu partition, not Windows. Log into Ubuntu, go to terminal and type update-grub; Now Windows shows back up in grub menu, continue with Windows 10.

Grub Boot Loader Windows 10

The TL;DR, added in the edit: The question is: How can I make the BIOS prefer GRUB over Windows Boot Manager on the same UEFI boot partition? The problem is not with Grub; Grub does the right thing when the BIOS starts it. The problem is not with 'the disk isn't bootable,' because both the Windows UEFI bootstrap and the Grub UEFI bootstrap are bootable.