"Microsoft is so much Bill Gates in terms of corporate personality," said Rob Enderle, an analyst at Enderle Group in San Jose. But Enderle noted that Ozzie was hired last year, when he sold Groove Networks to Microsoft, with the intent that he eventually would step into Gates' role as chief software architect. Gates likely judged that Ozzie had performed to his satisfaction and that "it was a matter of pulling the trigger and letting it happen," Enderle said.

He also pointed to delays in the development of Microsoft's upcoming Windows Vista operating system as a possible contributing factor. The Vista problems may have prompted Gates to "think it was time to make the transition," Enderle said. "Bill was a bit more distracted from the chief architect role than he should have been."

As part of the plan Microsoft announced last Thursday, Ozzie, who, like Gates, is 50 years old, took on the title of chief software architect. The company said Ozzie will work "side by side" with Gates on technical architecture and product oversight matters during the transition period.

New responsibilities

Mundie, 56, was given the new title of chief research and strategy officer and will gradually take over responsibility for the company's research and technology incubation efforts from Gates. In addition, Mundie will work with Brad Smith, Microsoft's general counsel, to lead its intellectual property and technology policy initiatives.