Head of Microsoft Windows is out Microsoft Corp."s Windows President Steven Sinofsky is leaving, allowing Chief Executive Officer Steve Ballmer to overhaul management of the flagship operating system in his push to win back personal computer market share. Sinofsky's duties were reassigned to Julie Larson-Green, who will take charge of all software and hardware for Windows, and Tami Reller, who will add oversight of the Windows business to her responsibilities in marketing and finance, the world's largest software maker said yesterday in a statement. They will report directly to Ballmer, effective immediately. The company had grown concerned over Sinofsky's ability to get along with other executives, including Ballmer, a person with knowledge of the matter said. Fresh on the heels of the release of the latest version of Windows, Ballmer is putting in place a new team to start planning the next upgrade, this person said. He's using new products and management shifts to help Microsoft withstand pressure from Apple Inc. and other mobile device makers that are winning over consumers and businesses. "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," Michael Gartenberg, an analyst at Gartner Inc., said yesterday. Microsoft is going to enter another period of management transition. Redmond, Washington-based Microsoft fell 3.9 percent to $26.89 at 9:35 a.m. in New York. Through yesterday, the stock had climbed 8.7 percent this year. A 23-year Microsoft veteran, Sinofsky is departing less than a month after the release of Windows 8, the latest version of the computer operating system, and Surface, the company's first foray into the tablet hardware market. The timing of his move is unrelated to the quality of the products or their reception in the market, said the person, who asked not to be identified because the matter is private. Sinofsky, who joined Microsoft in 1989, had spent most of his career working on the Office suite of products until he shifted to Windows in 2006. He stabilized that division after Vista, an earlier iteration of Windows, met with poor reception. Once considered a possible successor to Ballmer, Sinofsky more recently had failed to stem the loss of PC customers to rivals, including iPad maker Apple. Revenue at the Windows division had fallen short of analysts" estimates in six of the past eight quarters amid lackluster demand for PCs and a shift in consumer preferences toward handheld devices. He failed to receive all of his bonus for fiscal 2012 in part because a 3 percent decline in sales at the Windows division and the company's failure to meet requirements of a 2009 agreement with with the European Commission, according a regulatory filing last month. Female Engineer Larson-Green, who joined Microsoft in 1993, had been vice president of program management for Windows and was one of the executives who came to the division with Sinofsky from Office. Already one of the highest-ranking women at Microsoft, Larson-Green led the team that overhauled the design of Windows 8, opting for a start screen with tiles similar to the look of Windows Phone and eliminating iconic elements like the start button. Before that, she remade the look of Microsoft's Office software for businesses by switching from drop-down menus to a bar across the top called the ribbon. Larson-Green was in charge of all program management, design research and development of all international releases for Windows 8. She holds a master's degree in software engineering from Seattle University and a bachelor's degree in business administration from Western Washington University. Fostering Collaboration Like her former boss, Sinofsky, Larson-Green also turned to former Office colleagues. She recruited Jensen Harris -- who had helped her develop the ribbon in Office -- to direct program management for the Windows User Experience. Harris and Larson- Green are so close they finish each other's sentences, the two said in an October interview. Larson-Green is known for her ability to collaborate and get other people to work together, said the person with knowledge of her promotion. She needed Sam Moreau, who was given oversight of Windows 8 design, to form a bond with Harris, Larson-Green said in the interview. To break the ice, she sat the executives in a room, placed a bottle of wine between then and told them to get to know each other, Larson-Green said. Reller joined Windows in 2007 from the Microsoft Dynamics Division where she held a series of leadership positions. Microsoft promoted her to lead marketing and finance for the Windows business in 2009, reporting to Sinofsky. Reller began her career in technology at Great Plains Software Inc. in 1984 while she was in college, and was the company's CFO when it was acquired by Microsoft for $1.1 billion in 2001. She has a bachelor's degree in mathematics from Minnesota State University Moorhead and a master's in business administration from St. Mary's College in Moraga, California.