Well once I contacted the Windows support, and the guy on the telephone even said they will sue me, because I had as private consumer a business licence (my brother owns a pc shop and I help him out now and then). I told that guy on the phone to f**k of and should try, I didn’t break any legal rules and if he is going further I will sue them for unappropriated product marketing. After that the supporter hang up the phone and I never heard anything back.
Back then I build up a new computer and wondered why I could not activate the key, afterwards I read somewhere on the internet, that you can’t transfer a upgraded Windows Key to a other computer! You need to buy new one!
After some googling I found a shop which is selling Win 10 Keys for 20 €. I bought one there and had no problems so far. Link to the Shop: [Link removed]