So I take my 'puter to get a new motherboard. The place says okay we fixed it! Got it home, it fired up once. Took it back and four months later they said "we'll find one just like it and sell it to you". I said fine, unwillingly, but told them I wanted the OS from my hard disk on the new one. I expected them to clone my hard disk to the new one. What do they do? Put a pro version of the OS I had on the hard disk with that hacker proggy kmsauto. Piss me completely off. I have zero spare dollars to buy an OS much less a new computer. What would be the best way for me to get my old legal version of the OS onto a new hard disk so I can stop using an illegal copy? I'm okay with cracked software and stuff- just not the OS and not when I didn't ask for it. Know what I'm sayin'?
There’s a lot of gray area here. Is there a CoA sticker on your machine denoting the license? Where did you get Windows from in the first place? I assume you’re using Windows 7. If you have an OEM then it’s tied to your hardware and not legally transferable... though it could probably be done. If it’s a retail version, you can. In either case, though, you need the key.
https://www.makeuseof.com/tag/how-to-make-your-windows-7-pc-genuine-again-after-a-hardware-upgrade/
In any case, what they did is illegitimate if you’re describing this correctly. Sometimes the license doesn’t transfer or you simply cannot clone your existing installation onto new hardware.