win XP

I've been using the same xp for over 2 years, alway's "authentic" till a short while ago, when I've been getting a popup saying that it's not Authentic, but whn I click on the bubble it say's I do got a valid version, wtf? how can I get rid of the popup and startup popup? I don't care if it's legal, I'm not forking out another $200 for something I already have.

Call to Microsoft support i guess
Or install windows again, and don't install any updates, but get Autopatcher instead, the project is now suspended but you can find latest version somewhare on the internet...