Windows 8.1 Formatting

[DopplerY]

Hello, 

 

So I just upgraded my motherboard and my sistem is working fine like I didn't change anything, but I wanted to format my whole PC just because I have it for a while now.

 

My question is: if I make a bootable usb with the Windows 8.1 just like I did when I upgraded from Win 7, am I going to be able to use the same product key I've used before?

(the usb was created by using the command prompt and after tipping 'diskpart' and selecting the right disk  I just tipped 'create partition primary' and 'format fs=fat32 quick' and 'active')

 

Now I'm assuming this is possible but I just want to be safe. Also, I wonder if indeed it is, how does these keys work?

 

One last thing should I just use the Reset PC option to do this?

 

I did not find any posts similar to these one so if there is one please show it to me.

 

Thanks!