There's a rumor going round, about a conspiracy between MS & Fiat to have a TBox in every car - a MS powered computer that controls everything from the headlights to the movie the kids are watching in the back seat.
Aside from the inevitable joke, do you really think MS would trust their OS that much themselves? I mean, you can believe Fiat would go for a thing like this, but MS has good lawyers. They wouldn't take the liability risk.
Besides, the only mention of anything of this sort on either the MS or Fiat websites is a Fiat press release from July 2004.