Kevin Johnson, the man most directly responsible for current and future versions of Windows, as well as Windows Live and Microsoft's online services, is leaving the company for a position at Juniper Networks. Johnson has been co-president or president of the Microsoft platforms and services division since 2005, and oversaw the Windows Vista launch, and he pushed the company to purchase aQuantive in 2007, and Yahoo! in 2008. That latter purchase, of course, has thus far been unsuccessful.

Microsoft won't replace Johnson immediately. Instead, Microsoft CEO Steve Ballmer will oversee Windows and Windows Live himself and split off the company's online services as part of yet other reorganization.

Ballmer will have three direct reports in the new Windows division: Steven Sinofsky (Windows client), Jon DeVaan (Windows core), and Bill Veghte (Windows Server). All are senior vice presidents at the company.

Better known for his marketing chops than technical acumen, Johnson joined Microsoft back in 1992 and worked mostly in sales and marketing positions. In 2005, he became co-president of the Windows division alongside the retiring Jim Allchin. After Allchin's departure in late 2006, Johnson became the president of the Windows division at Microsoft and led the company's efforts to purchase online advertising firm aQuantive.

Unfortunately for Johnson, he was responsible for Microsoft's online operations during a time of great struggle. He was central to the on-again-off-again efforts to purchase Yahoo!, and had reportedly told Ballmer that the transaction would be concluded quickly. (It's unclear if he actually uttered the phrase "greeted as liberators.") In the last quarter, Microsoft's online businesses lost $488 million, keeping the division's uninterrupted losing streak alive.