Microsoft's head of Windows and online operations Kevin Johnson is leaving the company to become head of Juniper Networks.
The Microsoft veteran, who had worked at the firm for 16 years and managed more than 14,000 employees, was a key player in the company's failed effort to take over Yahoo, which went awry when the valuation was called into question.
Johnson's division will be split, with Windows and internet operations now reporting directly to chief executive Steve Ballmer to “give more agility and focus in two very competitive areas”.
Ballmer said: “Kevin has built a supremely talented organisation and laid the foundation for the future success of Windows and our online services business.”
A successor for Johnson has not yet been appointed but Johnson's immediate reports will now report to Ballmer.
Johnson launched Windows Vista to consumers and commercial customers, resulting in record-breaking Windows revenue of nearly $15 billion in fiscal year 2007.
“Microsoft is a special place and presents opportunity to so many,” Johnson said. “I have been so fortunate to have experienced 16 amazing years of building Microsoft's business, learning from great leaders in the company and working with phenomenally talented people.”