You may have received the dreaded “Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key” error message after switching on your computer. This message means that the computer fails to startup Windows using its boot device. A simple explanation could be that you selected the wrong boot device in the computer UEFI setup (or BIOS). The solution in that case is to restart the computer, to enter the UEFI (or BIOS) configuration and to select the proper boot device.
But this message could also mean that the system partition has been corrupted and needs to be repaired. We will see in this tutorial how I did it with a few simple command lines.