Hi,
I bought a laptop with a Windows 8.1, what I upgraded to Windows 10 when it was free.
If I transfer this machine to my Macbook, do I need to activate again? If yes, what are the steps and where can I find my current key?
Hello LeventeK1, yes, you will have prompted to reactivate Windows 10 virtual machine on an another Mac after the migration/transfer. Please check out this article if you have an activation issue in Windows virtual machine.