usually leads to unofficial "crack" or "keygen" sites, which often host malware or deceptive links.
If it didn't come from the official store, it is likely a pirated key that will be blacklisted in the next update. Play smart, play safe.
If you do not yet have a valid key, you can obtain one through these official channels: PC Versions
The most expensive "free" key is the one that costs you your personal data. Do yourself a favor: skip the search results, visit the official publisher’s website, and buy the legitimate registration key. Your computer—and your conscience—will thank you.