Thank you for the straight answer! But how about if the existing build, but change the motherboard to new one (maybe same model, or different model), will windows still work ?

Thank you so much for the guide!

I logged into my MS account (which I tend to forget over and over again and retrieved), and noticed that it has all my devices listed there: My current laptop, My Old PC, and even my old Lumia phone !!

So for my old Pc (as screenshot below), is the PC that I have already wiped clean, formatted, and Motherboard has spoiled. I am selling the remaining parts to someone else, which I am not sure if he will repair the MB and resell it as a whole system, or just savage the parts separately.

My question now is: if the buyer repair/change a new motherboard of same model, when he install new windows, will the windows automatically uses my original license? Or it wont, unless he log in using my MS account?

I will probably build a new pc next year, so I won't be able to test if the license can be successfully transfer over to my new build. But looking at my account under devices, my old PC license should have successfully linked to my MS account. So do I need to "remove pc", so it knows that this pc no longer tied to this license, and then only I can apply the "floating" available license on my new pc next?

Sorry I hope I ask the question correcltly.. 

It is from the custom build pc shop (not like dell, acer, asus those branded one)... It does come with a box , cd and series numbers all these. But it is written OEM system Builder Pack (Intended for system builders ONLY)