Can a retail version of Windows 10 that was upgraded for free from retail 8.1 be transferred from my current system to a new one? i.e. Is it possible/within the EULA. If so what is the best was to go about it, assuming the new system will use a different MS account (so the activation won't be transferred digitally with that)? Can I activate using the appropriate 8.1 key? I've tried googling the answer but found mixed messages.