I have bought a laptop that came preinstalled with Windows 10. I installed a Linux distribution as dual boot and then installed VM Ware on Linux. Then to use Windows just for a few occasions and to test things quickly without having to reboot all the time, I installed Windows 10 Home with the product key that was baked into my ACPI (The windows key that I would otherwise never see because it's OEM). Now windows swallowed the product key just fine, but now it asks for 'activation'. It says the product key is already in use. But it's on the same computer. I know that windows doesn't know that. But I really, really don't want to buy windows just to use it in a VM on a machine that already has windows installed. That would be just ridiculous.
I know there is this question, which is quite similar, but I don't want to deactivate my other windows.
I was able to go to activation and enter my Microsoft account details after saying "I changed my Hardware", and I guess I could kick my real windows on my laptop off the device list and deactivate it. But again, I want to use the same key for both windows versions on the same computer.
After a chat with some Microsoft guy, we ended up with: "Buy another license or deactivate your non VM windows. Frequent switching might cause microsoft's servers to automatically respond.", presumably with locking out my product key altogether.
So I'm open to more 'creative' and unofficial solutions now. After all this is my computer and I can do whatever the hell I want with it.