Microsoft's global marketing leader, Mich Mathews, is prepping to leave the company this summer after more than two decades at the tech giant.

She announced her retirement last night to company executives and will be helping Kevin Turner, Microsoft's chief operating officer, to whom she reports, and Microsoft CEO Steve Ballmer find her replacement.

Ms. Mathews oversees more than $1 billion in annual marketing spending for the Redmond, Wash., tech company, including Microsoft's consumer brands such as Windows, Bing and Xbox.

Speaking by phone this morning, Ms. Mathews said she made the decision to leave Microsoft over Christmas holidays, and doesn't have a new job lined up. "Twenty-two years in one place ... I feel like I've done so much" and "frankly it's time to do something new. It's half a lifetime. Microsoft was chapter one and it's time for a chapter two." She said she needs a break as well. "It's going to be awesome to actually get off the grid."

She first started working with Microsoft in 1989 after a stint at General Motors, and for nearly four years worked with Microsoft as a consultant in the U.K. She took up there full-time in 1993 when they asked her to lead the company's corporate PR function. By 1999, she was named an officer of the company, and from then on rose through the marketing ranks at the company.

In her post as senior VP-central marketing group, she was responsible for overseeing Microsoft's internal communications and external communications to consumers, the latter via advertising, public relations, events and packaging.

The timing of her departure is an indication Ms. Mathews felt she had unfinished business in redoing the company's media agency relationships. It decided to tap Publicis Groupe's Starcom Mediavest to handle U.S. buying duties and global planning and strategy, but kept on the incumbent, Interpublic Group of Cos.' Universal McCann, to lead buying duties in some 35 markets outside the U.S. She said: "I had to see that through."

"In the last several years I've very deliberately been changing our agency model. ... We have an agency roster with very big global reach which is important for us," Ms. Mathews said. "That's something we're going to be doing every several years and that's particularly important in the world of media and creative today because it's changing rapidly and you have to constantly be asking, 'Do we have the right model?' 'Do we have the right marketing mix?'"

She said she is not in a hurry to re-emerge, and she has "no limitations" about her next post in terms of geography or the type of company she'd like to work for. "I am going to talk to a lot of people, return all those calls I've never returned, take the summer and dive into something probably around the fall time frame."