I have two PCs. For the first, which was blank, I bought a retail copy of Windows 7 Home Premium and installed it a few years ago. Then, when the Windows 10 free upgrade was announced, I waited a few months before upgrading it to Windows 10. I just checked, and that PC's Windows 10 doesn't use the same product key as was used for the Windows 7 install. My second computer came with Windows 8 and was also upgraded to Windows 10. I'd like to virtualize Windows 7 on my second PC, probably with VirtualBox, and I know that virtualized Windows needs a product key like any other version of Windows. Since my first PC was upgraded to 10 and is no longer using that product key, does putting the retail copy of Windows 7 that was on there into a virtual machine on my second PC count as a license transfer?
Research: This SuperUser blog post from 2011 says I get one transfer as long as I remove the software. I know that OEM versions of Windows are tied to their machine, but I used a retail version: http://blog.superuser.com/2011/04/06/microsoft-licencing-transferring-windows-to-another-computer/
This is the latest version of the license (I filled the correct information into the tool and it gave me a PDF), which seems to say that I get unlimited transfers. It also mentions that if I virtualize the OS, it can't be physically installed to a machine: https://www.microsoft.com/en-us/useterms
More SuperUser posts that are relevant but don't quite answer my question: Does the license allow me to run Windows 7 in a virtual machine and on the host?
How does Windows 7 licensing work for running the OS as Virtual Machines?
This website says that I can virtualize my old copy of Windows if the PC is now using 10. However, does virtualizing the old Windows 7 on a different PC than it was originally on count as a license transfer?: https://www.infopackets.com/news/9613/windows-10-upgrade-can-i-keep-my-old-windows-install