Weary of his grind as senior vice president for applications and the Internet client group, Silverberg says he opted to come back part time as a consultant to Steve Ballmer, who was making his transition to the role of CEO.

"It was something I had wanted to do for many years and finally had the time," Silverberg, 48, wrote in a recent e-mail. "I also did other traveling and spending time with my family."

Others have a slightly different version of what happened. Sources working at Microsoft at the time said Silverberg was caught at the center of some of the company's most intense battles, starting with internal competition between groups working on Windows 95 and Windows NT. When control of Internet Explorer was transferred from Silverberg to Jim Allchin in a 1997 reorganization, sources say, Silverberg decided to take a two-year leave of absence.

Regardless of the circumstances of his resignation, Silverberg had a phenomenally successful run at Microsoft. The nine-year Microsoft veteran and PC Magazine 1995 Person of the Year was responsible for promoting all aspects of the Windows business from 1990 through 1995. During that period, he increased the operating system's revenue from $50 million to more than $3.5 billion. Later, he served as a linchpin in the company's most profound strategic transformation--turning employees' ideological focus from the PC to the Internet.

Like many relatively young Microsoft alums, Silverberg tired of semi-retirement soon after achieving it. He quit his part-time consulting job in October 1999 and parted ways with Ballmer, though he says he still meets with him regularly as a professional colleague and friend.

In February 2000, he and other former executives from Microsoft and McCaw Cellular Communications started a venture capital firm called Ignition Partners. The Bellevue, Wash., firm, which closed a $285 million fund in December 2001, specializes in early-stage software, network infrastructure and wireless companies.

"I wanted to get back involved in building businesses," said Silverberg, who has a bachelor's degree in computer science from Brown University and a master's degree in the same field from the University of Toronto. "I had the opportunity to do so at a great company like Microsoft, and now I felt it was time to help others build leading companies. It's tremendous fun to work with start-ups and entrepreneurs, helping them achieve their dreams."