Hello wonderful people! The situation that I've created for myself is as follows.
I have a gaming computer on win10, that consists of a 500gb ssd that is the main drive for the winos 10 and another 1gb hd for misc programs and backups. So right now its solely a win10 computer. What I did is this, I unplugged both of those drives and plugged in a blank 500gb hd to install my Zorin 16 pro. I installed Zorin on it and everything works fine by itself. So its like my computer is a Zorin machine now with the other 2 win10 drives unplugged. I hope I'm not confusing anyone so far. So its like I have 2 separate computers, unplug the Zorin 16 pro drive and plug in the 2 win10 drives and I have windows again and visa versa.
My question is this, can I plug in all three drives at the same time and somehow choose which one I want to use at startup? I don't want to screw up either of these 2 installations by doing something that will damage anything.
The easiest way to do that without re-installing any bootloaders, is to just go into your boot menu and select the drive, for example on my gigabyte board i'd hit f12 at boot, then select the drive with Zorin to boot zorin, Windows Ect.
Most Bios will let you select a default boot device so you can go set which one you want to usually boot to, and then when you want to switch just manually select the other drive
Remember to disconnect the primary drive when installing the second operating system. Once installed connect both drives and use the bios to select the boot device as suggested in the previous post.
You may have to do some tweaking with EFI and CSM in the BIOS for both OSs to be able to boot if wanting to update GRUB. When you boot Zorin, open a terminal and enter:
sudo update-grub
When it runs hopefully it will pick up your Windows drives and add entries for them in GRUB so no need to use the BIOS function.