Windows 10: My computer crashed and a need a copy of my windows 10 product key for reinstallation

My computer came with windows 10 installed. My computer crashed and I need to reload windows. How do I get a copy of my windows key

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How to reinstall Windows 10 if my computers used the free upgrade from 7 and 8?

Will windows 10 still accept the license keys from 7 and 8 now if I reinstall my computer?

Does Microsoft keep a list of users who upgraded to Win 10 using their 7 and 8 keys so that when users need to reinstall windows 10 the old keys would work?

Do I need to call in Microsoft to ask them to activate my Windows 10 when I give them my win 7 keys?

Both computers are laptops. The windows 7 machine had the serial printed on the back, and I needed to enter that when I upgraded to 10. The windows 8 machine had the serial built in inside its boot system so I didn't need to enter the key when I upgraded to 10, but I did manage to write down the keys using a fetcher program.

 

Reinstall Windows 10 Product key wont work

So the last update from windows 10 caused my computer to crash so I had to reinstall Windows 10. As of right now it's showing its not activated and that it needs a product key. I still have the product key of when I first purchased Windows 10 but I get
an error and it says that the product key cannot be used I need a new one. So should I purchase a new copy of Windows? Or is there an easier way to fix this I still have the original DVD and everything any suggestions?

 

How to reinstall Windows 10 if my computers used the free upgrade from 7 and 8?

Your ild keys should work but if you registered the key to your online ms persona (email address) it should be tied to your account , install without a key login with your credentials , then activate.