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The abrupt departure has many questioning the success of Windows 8, Sinofsky's relationship with Microsoft CEO Steve Ballmer, and the evolution of the software giant.
"It is a little surprising to see a departure of someone at this level in charge of so many products with such immediacy, with no transition period. Microsoft is going to enter another period of management transition," Michael Gartenberg, an analyst at Gartner Inc. told Bloomberg News.
During his tenure at Microsoft, Sinofsky won accolades for leading intricate software projects and making sure they were delivered on time.
It had been widely speculated that Sinofsky, a 23-year Microsoft veteran, would take the reins when Ballmer stepped down.
But according to insiders, Sinofsky and Ballmer didn't always see eye-to-eye.