Sorry for the confusing title I have no idea what to put there.

But the situation is that I reinstalled windows 10 on my friend’s laptop because he got the annoying ‘Activate Windows’ watermark, so I thought installing fresh windows 10 onto the laptop would solve the problem. But today my friend messaged me saying that the watermark is back even though the windows 10 that I installed was fully functional after I’ve done the fresh install.

What should I do to fix this? I have no idea what to google and it’s not helping much.