Steven Sinofksy, president of Microsoft's (Nasdaq: MSFT) Windows Division, has left the company 23 years after joining Microsoft as a software design engineer. No reason was given in the company press release.

"It is impossible to count the blessings I have received over my years at Microsoft. I am humbled by the professionalism and generosity of everyone I have had the good fortune to work with at this awesome company," Sinofsky said in the press release.

Two employees inherit Sinofsky's duties as president of Microsoft's Windows division. Julie Larson-Green is being promoted to handle Windows software and hardware engineering, while Tami Reller will expand her role to take command of business and marketing strategy. The changes are effective immediately.

Windows is Microsoft's third-largest division. Revenue from OS sales fell 33% year over year in the fiscal first quarter as customers waited to upgrade to Windows 8. Operating income fell 49.7% over the same period.

In a memo to staff published by AllThingsD, CEO Steve Ballmer focused on Microsoft's recent accomplishments:

We are facing a time of great opportunity. What we have accomplished over the past few years is nothing short of amazing, and I know we have more amazing in us. I am excited about our people, I am energized by our ability to change and grow, and I look forward to the success which lies ahead. Thank you for all you do, and please join me in congratulating our new leadership and celebrating all that we have accomplished so far.

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