Windows 10: Reinstall win 10

When i did reinstall, did i need new key because I have an original on my computer.

:)

 

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.

 

Fresh Install of Win 10 without Serial Key?

Looking to reformat a laptops HDD, and then reinstall Win 10 fresh. The problem is it came pre-installed with Win 8 and I did the free upgrade to Win 10. How exactly would I re-format the HDD, reinstall Win 10 and ensure it reactivates properly? I don't see a Win 8 serial key anywhere in the contents of the box.

 

Wipe a dual boot machine and reinstall Win 10?

I have an old machine that started out on Win 7. I updated/upgraded over the years and it now has two SSDs one with Win 7, the other with Win 10. I created the dual boot a long time ago from the Win 7 drive.

I'm worried wiping will negate my Win 10 lisence since it was an upgrade not the original OS. I have the original Win 7 serial, but I don't think that is relevent to the process any more.
At any rate, I'd like to give the machine to an elderly neighbor, so I need to wipe it and reinstall Win 10. I don't know where to begin. Anyone able to point me in the right direction, for a step by step?