I had recently installed Linux in a dual-boot setup on a test machine (an old Lenovo Thinkpad T430). What proved more difficult than in former times was to restore the original state. Most of the recommendations I found online were less than helpful. In particular, many of them ignored the fact that there are two entirely different approaches out there to handle the boot: UEFI and legacy or GPT and MBR respectively. My machine was using MBR (Master Boot Record), given its age.

What finally solved the issue was the following command:

C:\> bootsect /nt60 c: /mbr

I used a USB stick with Windows 10 Installer, but since then learned that you can get to the “repair” console easier, if your Windows 10 still starts. All you need to do is perform the following steps:

• Log off.
• When the login screen appears, press a key so that the password field shows up. This will also enable the “power” button in the lower right corner of the screen.
• Press and hold shift
• Left-click the power and choose “Restart”
• Let go of the shift key and the repair menu appears.
• Go to Troubleshoot > Advanced options > Command Line