The Microsoft co-founder is scheduled to end his day-to-day executive duties at the end of June, but he will remain chairman and he's expected to continue working on selected projects.
Microsoft has been preparing for Gates' shift to philanthropy since 2006, when the plan was announced, and it has already installed executives Craig Mundie and Ray Ozzie to fill his roles in the business, working with Microsoft chief executive Steve Ballmer.
"I don't think the departure will be too disruptive - it's not like it's a complete severing of the relationship," said Dwight Davis, an analyst at the research firm Ovum. "But nonetheless, that's going to be a notable milestone in the coming year for Microsoft, one that will alter the company's profile in a fairly significant way."
Although the transition may be fully planned out, this is a difficult time for Microsoft, with reception of its Vista OS tepid at best, and with the challenges of upstart Google.