I ended up with a crippling infection on one of my two laptops. I Dban ed it and reinstalled from scratch, but it wouldn't accept the product key that came with the laptop (pre-install), so I entered the key that came with the disk which I bought (Win 8.1 home). I bought the disk for the purpose of reinstalls, and the key I used pre-install is the key being used by my other laptop. When I tried to switch keys on my other laptop, it said that key was being used by another computer. Do I have to de-activate the key or something? I have two legit keys and two laptops, how do I make this work?