Steve Sinofsky is probably the second most important figure at the company after the chief executive Steve Ballmer.

BBC: Windows boss shown the door

The Surface will "be priced like comparable tablets, " Windows Chief Steve Sinofsky said.

WSJ: Microsoft Unveils Surface Tablet to Rival iPad

Although it features a quote from Steve Ballmer expressing gratitude for Sinofsky's years of work and another from the man himself talking of the professionalism and generosity of everyone at "this awesome company", there is no explanation of why he is leaving.

BBC: Windows boss shown the door

However, one industry watcher suggested there had been talk of an internal "war" between Mr Sinofsky and chief executive Steve Ballmer.

BBC: Steven Sinofsky

Based on the internal memo and the public comments made by both Sinofsky and Microsoft CEO Steve Ballmer, it is clear that he was not fired.

FORBES: Scott Forstall and Steven Sinofsky's Next Job

So perhaps Steve Ballmer was rather relieved when Mr Sinofsky talked of seeking out new opportunities.

BBC: Windows boss shown the door

He added that many observers saw Mr Sinofsky as a potential successor to Steve Ballmer, Microsoft's chief executive.

BBC: Steven Sinofsky