Seattle: Departed Windows boss Steven Sinofsky was the latest in a line of high-flying Microsoft Corp executives tipped to lead the world's largest software company at some point.
Microsoft has never anointed a successor to Steve Ballmer, who took over as CEO from co-founder Bill Gates in 2000 and shows no sign of moving on. Over the past decade, speculation has centred on a number of potential candidates, but they have all left the company.
Steven Sinofsky: The highly successful but confrontational head of the Windows unit left abruptly this week by "mutual" agreement. He has not announced a new job.
Ray Ozzie: The software guru tapped by Bill Gates to take over his role as Microsoft's big-picture thinker left to start his own project in 2010.
Stephen Elop: The head of Microsoft's Office unit, its most profitable, took the job of CEO at Finnish phone maker Nokia in 2010.
Kevin Johnson: Windows and online head went to run Juniper Networks in 2008, largely taking the blame for Microsoft's failed bid to buy Yahoo.
Jeff Raikes: Veteran sales and marketing leader and head of the Office unit left to join the Bill & Melinda Gates Foundation as CEO in 2008.
Paul Maritz: One of the key powers in the early days of Windows left in 2000, eventually becoming CEO of PC virtualisation firm VMware. He recently became chief strategist at EMC.