After 21 years working with Microsoft and spearheading development for Windows Phone, Charlie Kindel has suddenly resigned, leaving Microsoft to start a new company on his own.

Kindel announced on his personal blog of his plans to leave Microsoft in early September to start a new company, in which no details were enclosed. Though he is "not yet ready to disclose details about the new venture," Kindel mentioned it will encompass mobile, social networking and cloud along with sports and advertising.

In an email entitled "Goodbye Microsoft - After 21 Years It's Time To Move On," Kindel reflected upon his time at Microsoft since he began right out of college at the University of Arizona in 1990, working on numerous projects which he lists.

"Back in 1990 I assumed I'd work here for 3 or so years....I never had the need to look outside Microsoft because I kept finding one challenging opportunity after another," Kincel said. "Microsoft enabled me to see the world and I'm grateful for that."

As general manager for development, Kindel headed a team that created a new operating for Windows Phone, calling it "The BEST product Microsoft has ever built." He advised his team not to "let up" developing the Windows Phone 7, which recently has plunged by 38 percent in the smartphone market since its launch in November last year.

Kindel, however, did not attribute his resignation to the Windows Phone but rather his intentions to begin a new company based in Seattle.

"I have finally decided I need to do something different: I'm leaving to start a new company here in the Seattle area," Kindel said. "I'm sure you'll hear about it."