Microsoft: What went right under Satya Nadella?

On Monday, it will be five years since Satya Nadella was announced as Microsoft's chief executive. Since taking charge he has turned the tech firm's fortunes around, making it the most valuable company in the world for the first time since 2002. You thought Microsoft was so last century, didn't you? In the late 80s and 90s, the company's Windows operating system ruled the world. But where Bill Gates - chief executive from 1975 to 2000 - caught the wave of personal computing, so Steve Ballmer - 2000 to 2014 - failed to do likewise with mobiles.