Bangalore: After a series of undisclosed happenings inside the software giant, Steven Sinofsky, the head of Windows operating system, who was said to be Microsoft's CEO-In-Waiting has suddenly left the company.

Microsoft has not yet given any clear explanations on Sinofsky’s departure except Steve Ballmer, the Chief Executive saying "Sinofsky has decided to leave the company." But according to BBC, the exit of Window’s head just weeks after the release of company’s flagship OS, came after an internal "war" between Sinofsky and Steve Ballmer.

Brendan Barnicle, an analyst at Pacific Crest Securities, who responded to BBC, underlined the reaction of entire industry watchers: “This is shocking news. This is very surprising!”

In a letter to his colleagues, Sinofsky said, "Some might notice a bit of chatter speculating about this decision or timing. I can assure you that none could be true as this was a personal and private choice that in no way reflects any speculation or theories one might read - about me, opportunity, the company or its leadership."

Eventhough Sinofsky quelled the rumors of his departure with this letter, another report from Business Insider said Sinofsky wanted to be designated as Steve Ballmer's successor after Windows 8 ships, and he had threatened to quit if he didn't get the nod.

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The departure of this big time executive, which Microsoft announced will be “effective immediately,” is raising concerns about the future of Windows 8 and Surface tablets. After the announcement, Microsoft’s market cap has been reduced by more than $10 billion.

The company has promoted Julie Larson-Green, the corporate VP of program management for Windows to lead all Windows software and hardware engineering.