I not want to transfer on a new PC. I want upgrade MotherBoard (o replace if broken) of my existing PC.

So you tell me that :
Win8 upgrade tell me a license key that need to find old XP
Win10 key that Microsoft send me after upgrade from 8.1 can also be used on new hardware from scratch but maybe i...

My problem is bigger.
I have a windows 8 license that is an upgrade that Microsoft did in past (promotion low price for decrease license xp number in teh world) for Wxp license.
This W8 license...