Former Windows chief Steven Sinofsky has joined venture capital firm Andreessen Horowitz as a board partner.

“In this position I will represent the firm on the boards of portfolio companies when the opportunities present themselves, but will not be a full-time member of the firm,” Sinofsky wrote in a blog post(Opens in a new window).

Sinofsky acknowledged that he’s “relatively new to the VC world and have a lot of learning to do—and I am very excited to do that.” He said he first got to know Marc Andreessen and Ben Horowitz late last year, and was impressed by the “commitment to fostering innovation, product creation, and working with product-focused entrepreneurs.”

He also wanted to work with those who valued teamwork and were in it for the long haul. “Scalable work that ‘goes big’ requires a lot of people. Being part of a team that works to let each person contribute at their highest level is how the resulting whole is greater than the sum of the parts,” Sinofsky wrote. “Sustainable efforts take more than one turn of the crank. The commitment to the long term that starts from building strong relationships through supporting entrepreneurs as they create sustainable products and businesses truly differentiates the a16z approach.”

Sinofsky said he will bring his expertise in “working to change the rules of the product game” to Andreessen.

Sinofsky left Microsoft in Nov. 2012, shortly after the launch of Windows 8. He worked on development and marketing of Microsoft’s flagship product for more than three years, having joined the company as a software design engineer in July 1989. According to reports, the Microsoft executive’s departure “came amid growing tension between Sinofsky and other top executives.”

In December, he announced that he would head to Harvard Business School in the spring of 2013 to teach “product development” and write articles about the topic. Sinofsky said today that he will remain at Harvard and “continue to pursue other business and product development opportunities that arise.” Ultimately, he will be “transitioning to the Bay Area full time” rather than living a bi-coastal life.

“I will still definitely explore companies out East, but maintain a strong focus on the Bay Area,” he wrote.

For more, see what Sinofsky had to say during an appearance at May’s D11 conference.