do I actually have to call Microsoft on the phone?

If I want to change the motherboard (essentially: replace the notebook) for the same serial number, do I actually have to call Microsoft on the phone? Once, or every time I have anew machine? What's the current state of affairs?

If you have a transferable Windows license and you change your motherboard (or make other significant hardware changes) you'll have to call them (every time in my experience).

Type slui 4 in run box and follow the instructions. Generally you'll only "talk" to a robot and type in the long string of numbers slui 4 gives you on your keypad and your code will be returned. You can use Skype and it gives an option to get the number back on your smartphone (but I've not tried that so not sure how it works).

It doesn't take long.

@lx07

How painful or painless is this experience of calling them? Then what exactly happens - from a purely technical perspective? You have your Windows 10 ISO with your valid key which you can't install on your new machine. You call them on the phone -> [Magic happens] -> then all of a sudden, you are able to install Windows 10 on your new machine.

I have had to do this after bricking the bios on one of my computers a few years ago. I simply called them after I replaced the motherboard and told them my windows key, it was a long time ago, from memory they guided me through a process and asked me to type in a new key. Took less then 5 minutes and there was no remote access or anything like that

With 10 if your key isn't accepted on install you would click on "I don't have a key" 10 would install but not be activated.

You run slui 4 and enter the Installation ID shown on the screen (9 blocks of 6 numbers - it is not the same as your Windows key). This normally returns a Confirmation ID automatically and you type it in. Sometimes it will not and you are put through to a real person and you can explain your situation to them.