The Microsoft Corp. executive who led the company's challenge to Google is leaving the company.

Christopher Payne, the corporate vice president for Microsoft's Live Search initiative, plans to launch a Seattle-based technology firm unrelated to the search business, a person familiar with the situation confirmed Wednesday.

Under Payne's leadership, Microsoft's search site has lost market share since the company launched its own homegrown search in early 2005, attempting to challenge Google. However, the person described Payne's departure as a "personal decision" that he made "to go off and do something entrepreneurial."

A Microsoft spokesman declined to comment, and Payne wasn't available. A replacement hasn't been announced. In an interview with the Seattle P-I a year ago, when the company launched a second version of its search technology, Payne acknowledged that Microsoft needed to show improvement in market share.

"I'm hoping this does turn it around, without a doubt," he said at the time. "We believe that it's still very early in search, and that there's still significant room for differentiation. Prior to this, I don't think we've really gotten enough differentiation in order to win people back."

Since then, the volume of queries conducted on Microsoft's Live Search engine has remained flat, while Google and Yahoo have risen by 33 percent and 22 percent, respectively, according to Nielsen NetRatings data.

The company on Wednesday announced an executive reshuffling that includes bringing Brad Goldberg, a marketing general manager from the Windows division, into the Windows Live group. Earlier this week, Blake Irving, another Windows Live corporate vice president, told others at the company that he plans to retire later this year.

See earlier story: Microsoft falls further behind in Web search