That hesitancy to start anew at Microsoft makes perfect sense because Windows is by far the most successful software product in history. Why tamper with success? Especially with success that's unprecedented in business history?
Unless a company is willing to undergo self-induced "creative destruction," it's almost inevitable that success will create cash cows that nobody (management, investors and customers alike) are prepared to sacrifice.
Even now, it's going to be very hard for a new CEO at Microsoft to get the company to stop thinking about Windows and start thinking about something new. Unfortunately for Microsoft, in business, strengths eventually become weaknesses.
It's very different though, inside companies that have been on the brink, of financial disaster. It's easier to make a leap of faith when you've stared into the abyss.
The same thing is true of businesspeople. The best entrepreneurs are those who've failed at least once, because they've learned what doesn't work as well as what does. As a general rule, people learn more from failures than from success.
Failure teaches you to identify your weaknesses and use them to your advantage. For example, some of the most effective salespeople I've met are introverts who've learned to use their thoughtfulness to become better listeners.
Failure also teaches you to value your strengths but prevents you from letting those strengths make you muscle-bound. For example, I know a woman who's almost frighteningly charismatic, but she knows how to tone it down to increase her credibility.
There's nothing wrong about success. It's fun and wonderful and all those good things. But it's dangerous, too, especially for those who have never had the great good luck of having at least one huge failure.