The latest shake-up inside Microsoft involve Jeff Raikes, the head of the company’s $16 billion Office software business, who announced he would retire later this year, being replaced by Stephen Elop, the former chief operating officer of Juniper Networks.

Mr. Raikes, 49 will hand management responsibilities this month, although he will remain a member of the senior management group until his retirement in September to ease Elop’s transition, an e-mail to staff from Steven Ballmer, chief executive of Microsoft said.

According to Microsoft’ representative Bill Cox, Mr. Raikes, whose personal wealth is estimated at several hundred million dollars, has not revealed any plan of what he is going to do next.

Mr. Raikes, a Stanford University graduate who was raised on a Nebraska cattle ranch and a part owner of the Seattle Mariners baseball team, is the third-longest serving executive at Microsoft, the world’s largest software maker, joining the company in 1981. He was recruited from Apple Inc. where he worked for less than two years. As one of Microsoft’s three presidents, Mr. Raikes leads a unit that accounted for 32 percent of sales last fiscal year.

"For more than 20 years, he has been the chief strategist behind the establishment of our information worker business. He will be greatly missed when he retires from the company next fall," Ballmer said in the same email.

Michael Gartenberg, an analyst with JupiterResearch in New York said that Raikes’ departure is “really a big loss” for the company.

In almost all of his career, Mr. Raikes helped building Microsoft’s Office business, including its popular word processing, Excel spreadsheet, presentation and e-mail program, declaring himself proud of the fact that more than 500 million people are currently using the Office tools every day.

Mr. Elop, 43, who became first known as head of software company Macromedia before selling that business to Adobe System Inc. in December 2005 for $3.34 billion, will leave the position of chief operating officer at Juniper Networks, based in Sunnyvale, California.

Juniper’s representative Michael Hakkert said the company is already looking for someone to replace Mr. Elop, while Juniper’s shares fell 15 cents to $30.67.

Mr. Elop will join Kevin Turner, who joined as chief operating officer from Wal-Mart, chief financial officer Chris Liddell and chief software architect Ray Ozzi, all of them being chosen from outside the company that had previously recruited its senior management internally.

Mr. Elop comes at Microsoft’s running at a time when the company is facing competition from Web service providers like Google Inc., which are offering a rival product for free to use on a Internet browser. Microsoft also competes with Adobe’s Flash and Acrobat software and Cisco Systems Inc.’s programs that allows workers make phone calls and hold teleconferences on the web.

"He's going to have to manage an orderly transition where Microsoft takes what's fundamentally a successful desktop product and moves it in bits in pieces to the Web--cannibalizing itself without shooting itself in the foot, and insuring that it isn't cannibalized by others," Rob Helm, director of research at Directions on Microsoft says.

The news of Mr. Raikes’ leaving Microsoft comes after Bill Gates already announced that he would step down from Microsoft’s chief software architect in July.