If you previously purchased a legitimate retail license for Windows 7 or Windows 8, you can use that same product key to activate Windows 10 for free. This is a great way to get a legal activation at no extra cost.

KMSpico explained: No, KMS is not “kill Microsoft” - ThreatDown

Searching for "KMSPico Windows 10 download softonic full" often leads to numerous, often fake, "official" websites.