Can i get the initial OS that came with my laptop?

hadesambrosia

Estimable
Sep 22, 2015
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I have a lenovo y50 which i bought second hand. It was only used for a month or less and came refurbished so it was pretty new. Now when I got it I needed to format it because there was a bunch of applications on it. I gave it to a friend to do it and he formatted my laptop without backing it up (it came upgraded to windows 10 from 8.1) and installed win 7 on it that wasnt activated. I upgraded to win 10 and it was activated initially but now it isnt and tells me that my key isn't valid. Is there a way I can get the activation code from the laptop itself? Or is there a way I can get it back to its original os win 8.1? Really need advice, this issue has been bugging me for a month now.