I don't see why not, as long as the license for that key matches the OS.
A friend of mine used to buy COA stickers from eBay that had XP keys on them for like $10 each. They are OEM keys so he used an OEM XP CD-ROM to install them with the keys on used systems. They would activate even if they have been used before. If activations run out you can call Microsoft and have them reset.
Windows 10 Keys are different, locked to the hardware. Windows XP keys can be transferred to a different system.
XP has some kind of hardware check too. I had to use a key off the internet when I cloned an ancient PC into a VM because it wouldn't accept the original key.
Depends on the type of key you have. If it is a PRO(i am assuming that's the version of OS)/non-OEM license, then you shouldn't have a problem. Definitely worth a short though.
In a word the EULA says you can't transfer a license to a different PC, but it hasn't been tested in a court yet. People have transferred an OEM license and activated it. So it can be done, but the question about it being legal might vary by nation as Germany allows it if other nations do not.
But since it hasn't been tested in a court yet, nobody can say how legally binding it is or is not.
Agreed on not tested and my philosophy with legal grey areas is to avoid being part of the test case... However, these specific images come with their own EULA that says that you can not apply a different license to them (I checked because I would have also liked to have done so if it were allowed).
Just use this as they suggest for testing. Keep your data elsewhere and roll back/re-install every few months.
