You just can't stand the idea that MSFT will never go out of business. In the worst case scenario all their consumer business dries up and they become IBM.
Windows share of the market may be in decline, but there is a long tail on it. Indeed possibly the consumer business will dry up in favor of services aimed t the enterprise, but MS has put so much money in the Xbox, Kinect etc. its hard to imagine them abandoning it any time soon.