Former Windows President Steven Sinofsky has joined Andreessen Horowitz as a board partner, according to an announcement he has posted to his well-known personal blog, “Learning by Shipping” this morning. The new VC will represent the firm on the boards of portfolio companies, as the opportunity arises, he says, but will not be a full-time partner.

He writes:

I’m relatively new to the VC world and have a lot of learning to do—and I am very excited to do that. I can’t think of a better place to do this than a16z, as they share the commitment to learning and sharing that learning, for example through all the blog posts the GPs write. I first got to know Ben, Marc, and some of the over 70 people at the firm starting late last year. What was so cool to see was the commitment to fostering innovation, product creation, and working with product-focused entrepreneurs.

Sinofsky also explained why he believes himself to be a good fit at a16z, saying that his experience in product development has been focused “learning and changing from within an organization as part of teams.” At Microsoft, he led product development for Windows and Office, and was once thought to be a candidate for the position of Microsoft CEO. But Sinofsky was also polarizing, and  something of an outsider among executives. Eventually, he and Microsoft mutually parted ways, as Microsoft wanted someone who could work across product groups, and create a more elastic set of services for the cloud era.

Shortly after leaving Microsoft, Sinofsky took a position as EIR at Harvard Business School, which he now will continue. There, he teaches and writes about product development, planning, collaboration, and more. He says he will also remain open to other business and product development activities, as they come up.

According to AllThingsD, Sinofsky has been involved with Andreessen Horowitz since the beginning of the year, and has been advising its partners on various issues. This announcement now solidifies that activity into a more formal role. He’s initially focused on productivity software, but is open to other tech sectors, the report states.