How to boot into old operating system?

[hellopeops]

Greetings;

I recently assembled a new computer.

My previous system ran Windows 10; my new one runs Windows 11. My new system is up and running. I am trying to figure out how to boot into my previous operating system/drive. And it won't work. My current system won't recognize the previous operating system drive as bootable drive.

Is this not a possibility?

 

[hotaru.hino]

There's likely a difference in the boot configuration between the old system and the new one.

In any case, there's not much of a point to booting into the old OS from the new system. If it's data you want to pull, you can do that from the new OS.