EDIT: It did - changing that setting back to "AHCI" resulted in a, "This operating system failed to start", message when I tried to boot XP. Changing the BIOS back to the "IDE" setting didn't fix ...

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.

To fix Operating System Loader has no signature, Incompatible with SecureBoot, All bootable devices failed Secure Boot verification error, follow these steps.

If the previous steps did not fix operating system error in Warzone 2.0, you also need to make sure that Modern Warfare 2/Warzone 2.0 game is not set to run in compatibility mode.