> I had bought the laptop with windows embedded in it from an onsite seller (genuine HP seller).
> It was windows 8/8.1 then and i got it upgraded to windows 10.
When Windows 10 was first activated, you were granted a "digital entitlement" to reinstall Windows at any time, at no cost, onto the same computer.
> All was going good until recently i gave my laptop to a friend of mine.
> He has run some softwares or some unauthorized keys, which is now showing me to "Activate Windows".
Can you use "System Restore" to time-warp your computer back to a date before he mucked with it?
> Q1. How can i get my previous windows OS key so that i can legalize my copy of windows OS?
First, when you do try to activate, does it activate, or do you get an error-message?
Second, from a command-line prompt, what do you get from the command:
wmic path SoftwareLicensingService get OA3xOriginalProductKey
???
Third, there are free utilities to "peek" into the motherboard, to extract the original Windows 8/8.1 product-key.
> Q2. Once i get the key by the virtue of answer to the Q1 above,
> will my system continue with windows 10 or will it downgrade to Windows 8/8.1?
If the activation is successful, then the currently-installed Windows 10 will be activated -- not Windows 8/8.1.
If the (hidden) "System Recovery" partition on your disk-drive is still intact, and you run "System Recovery", then the original factory-loaded operating system, namely Windows 8/8.1, will be installed.
But, you can leverage your entitlement to upgrade to Windows 10.
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