1 Pc 2 Ssd. One W/windows 11 Pro, One With Windows 8.1

Geekom mini it13
lexar NM7A1 2tb Windows 11Pro
Samsung 840 1tb Windows 8.1
intel i9 13900H 2.6ghz

Not sure how to ask the right question on running 2 different OS on the computer.
I have 2 SSD ports and the system came with the Lexar and Windows 11Pro.
I plugged my old Samsung with WIndows 8.1 into the other port.
It shows both disks and info
I tried to boot the Samsung 840 during startup using the bios and it doesnt boot. Windows 11 boots
Is there a thread that shows how to run both systems on the same computer?
I have a couple programs I want to run from the old windows 8.1 that won't run on 11Pro.

 

I am not familiar with the bios in that, so can not speak to it. However, I have used Super Grub2 on a usb drive. It see's available boot drives, and lets you choose what you want to boot. It may work in your case. try it and see.
https://www.supergrubdisk.org/