To fix An operating system wasn’t found error on Windows computers, first check if the Disk Type is GPT or MBR, and then follow these steps.

If you see Error 1962, No operating system found, Press any key to repeat boot sequence when you start your Lenovo computer, see this post.

You can try to disable compatibility mode to fix the problem, as this guide will show you. How to fix Warzone 2.0 Operating System Not Supported error ...

On Windows 11 (and 10), automatic repair is a feature designed to troubleshoot and fix common problems preventing your computer from loading correctly.