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.

But can it fix the worst problems of the troubled operating system? Windows 8.1, as described in a Microsoft blog posting, offers plenty of nice fixes.

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 ...