Microsoft has announced that the head of its Windows division, Steven Sinofsky , has left the company with immediate effect .
The news of Sinofsky's departure comes less than a month after the release of Windows 8. With the company 23 years, Sinofsky was widely tipped to be the next chief executive of Microsoft
No reason has been given for his departure but the company has announced that Julie Larson-Green will be promoted to lead all Windows software and hardware engineering.
Microsoft CEO, Steve Ballmer, commented: "The products and services we have delivered to the market in the past few months mark the launch of a new era at Microsoft.
"To continue this success it is imperative that we continue to drive alignment across all Microsoft teams, and have more integrated and rapid development cycles for our offerings."
Ballmer added that he had the utmost confidence in Larson-Green, calling her "the best possible person for this job."
He had immense power as head of the Windows unit but was not known for working well with other executives.
Neither Microsoft nor Sinofsky explained the move although a Microsoft staffer , who asked not to be named, said the decision was "mutual".
"This is shocking news. This is very surprising," Brendan Barnicle, an analyst atPacific Crest Securities was quoted as saying.
"Like a lot of people, I thought Sinofsky was in line to potentially be Ballmer's successor."
The website ZDNet said some people on Twitter and email thought supposed poor early sales of Windows 8 and/or the Surface tablet were to blame. "I'm betting many Microsoft watchers on Wall Street will react similarly," said the writer.
But he said it was too soon to judge if Windows 8 and the Microsoft Surface tablet were successes or failures.
CEO Steve Ballmer, 56, shows no sign of leaving after almost 13 years in the job. He has now replaced all the leaders of Microsoft's five main operating units in the past four years.
He told employees in a memo on Monday simply that: "Steven Sinofsky has decided to leave the company."
In a later media statement, he added that it was "imperative that we continue to drive alignment across all Microsoft teams, and have more integrated and rapid development cycles for our offerings".