Install 2 Win 10 installations on 1 disk drive.

I have the iso for Win10 build 19043.1237 on a USB flash drive and I have a Win11 ready motherboard. For testing, I've installed Win10 multiple times on various disk drives and upgraded some of them to Win11.

Now I want to install Win10 twice on one disk drive. I plan on upgrading one of them to Win11. Has anyone installed Win10 on 2 different partitions on a disk drive? I've done it, but now the second installation boots up only. I expected an OS selection screen allowing me to chose which OS I want.

I've gotten such a screen when I installed Win10 on another disk. The installer made the other disk non-bootable and gave me the OS selection screen on the first disk. But I want to put 2 OS installations on one disk and get the OS selection screen.

When you are booted into one Windows installation, the other Windows partition should have a drive letter. If it does not, then simply assign it a drive letter. Let's say it is X: drive. The command to add it to dual boot would be:

Thanks for the reply. Actually I just remembered I failed to disable fast boot, which I do by shutting off hibernate. Now it's working, and I'm embarrassed. But I'm old so I have an excuse.