Microsoft's leading executive of its Windows division, Steve Sinofsky, is no longer employed by the company. The man, who has been with president of Microsoft's leading desktop OS for just over three years and has held a position at the company since 1989, said that he is "humbled by the professionalism and generosity of everyone [he has] had the good fortune to work with at [the] awesome company."

The Redmond-based corporation announced these leadership changes in a press release late Nov. 12. Its reasoning for such a move is unknown, though the title of the press release — "Microsoft Announces Leadership Changes to Drive Next Wave of Products" — suggests modifications are required to start the development of the company's upcoming products.

CEO of Microsoft, Steve Ballmer, wrote a farewell letter to Sinofsky. The Verge was able to obtain a copy and has shared it on its Web site. In the letter, Ballmer states that he is "grateful for the work that Steven has delivered in his time at our company," but it does not hint what happened between the company and Sinofsky.

Moving forward, Julie Larson-Green will be the president of software and hardware engineering for Windows and the company's CFO, Tami Reller, will be responsible for the business portion of the division. All changes are effective immediately, though it is unclear exactly when Sinofsky left the company.

Update: Paul Thurrott's SuperSite for Windows acquired a copy of Sinofsky's letter to Microsoft employees. He assures that there were no hard feelings and the choice was a personal one — he wanted to leave, was not fired, and the true reason is still unknown.

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.
Sources: Microsoft News Center | The Verge | Paul Thurrotts SuperSite for Windows