Microsoft self-sabotage?

Well, I had a fun little adventure in Ways Microsoft Can Break Itself today: I bought my laptop brand new almost 4 years ago. Besides a hard drive replacement almost 2 years ago and the slow but inevitable death of the original battery (replaced ~1/2 a year ago), it’s been blue skies. This morning, all of a sudden, it started saying that my copy of Windows 7 (which, of course, came preinstalled) “is not genuine” and that I need to buy genuine software. Say what?

Avast, Spybot, and Malwarebytes found no baddies besides a few unwanted but mostly harmless cookies. The internet said this has actually happened to quite a number of people. The most informative page (if it’s accurate) said Windows has a hidden function that gives Microsoft a snapshot of the hardware you’re running when you first set up the computer, and if too much changes, especially if it changes all at once, it flags you and thinks you’re trying to pirate/copy the OS onto new computers, or something like that. Suggestions included mostly “call Microsoft (ha ha like they’ll help),” “reinstall Windows (ha ha you lose anything not yet backed up and have to waste a day setting the rest back up)” or “buy a new copy of Windows (ha ha Microsoft just robbed you).”

Someone with apparently more sense suggested re-entering the product key from the sticker on the bottom of the laptop. I did. This seems to have fixed it, but I still have no idea what caused my OS to try to self-destruct or whether it’ll do it again. Hooray. -_-

(If you happen to know what causes this – when no hardware has changed – please tell!)