Windows Chief Sinofsky Leaving Microsoft Steven Sinofsky, the leader of Microsoft's Windows business, is leaving the company, just weeks after the company released the biggest overhaul in decades of its flagship product. Microsoft described the departure of Mr. Sinfosky, a 23-year veteran of the company, as a mutual decision by Mr. Sinofsky and Steven A. Ballmer, the chief executive of the company. Julie Larson-Green, another Microsoft veteran in its Windows division, will take over the leadership of all engineering responsibilities related to Windows. Tami Reller, the chief financial officer of the Windows division, will run business and marketing for the group. Mr. Sinofsky was seen as one of the most competent managers within Microsoft and earned high marks for helping to improve the quality of its software after the company released Windows Vista, a widely criticized version of the operating system. His name was often floated by people speculating about a possible successor to Mr. Ballmer, who has announced no plans to retire from the company. But Mr. Sinofsky was also a polarizing figure who alienated many other members of Microsoft's senior leadership team. For that reason, he was seen by many insiders as an unlikely replacement for Mr. Ballmer.