On Friday, the man most responsible for bringing Microsoft Windows into our homes and offices, forever changing the way we live and work, will leave Microsoft after 33 years at the Redmond, Wash., software Goliath. Bill Gates, 52, leaves behind his day-to-day responsibilities at the company he co-founded along with childhood friend Paul Allen in 1975 to become a full-time ambassador of the Bill & Melinda Gates Foundation in Seattle, which he and his wife established in 2000 to promote health and education worldwide.

Gates's history at Microsoft parallels that of the personal computer, which was little more than a tool for scientists and hobbyists before the Windows operating system made the PC accessible to everyone else. He eventually led a company that last year earned more than $51 billion, employed more than 78,000 people, and operated in 105 countries and regions worldwide. And he became quite rich—with an estimated personal wealth of $58 billion, which has afforded him the opportunity to become a philanthropist.

Microsoft is, of course, more than simply Windows, and Gates's drive to branch out into new areas such as word processing software, databases and Web browsers fueled the company's growth. This ambition also got the company into hot water with the U.S. Department of Justice (including one antitrust case that dragged on for six years), which has repeatedly accused Microsoft of locking out competitors by packaging its best-selling operating system with software such as its Windows Explorer Web browser and Windows Media Player (for playing audio and video files via a PC).

"Bill Gates is the quintessential risk taker," says Joshua Schuler, executive director of Massachusetts Institute of Technology's Lemelson–M.I.T. Program, a nonprofit organization that awards hundreds of thousands of dollars to inventors annually. "He understands that innovation is all about taking risks and being okay with the prospect of failure."

Under Gates' leadership Microsoft succeeded far more than it failed, transforming the computer from simply a number-crunching calculator into a platform for mass communication. This has proved to be essential to subsequent generations of entrepreneurs. "How many calculations for business plans have been created using Microsoft software?" Schuler asks. "Anyone has the capacity to be inventive, and Bill Gates and Microsoft created tools that are used to build, test and convey those ideas."

Scientific American has crossed paths with Gates a number of times over the years. Here's a sampling:

Gates's article in SciAm's December 2006 issue ("A Robot in Every Home") explored the promise of robotics as well as some of that technology's most pressing problems.

Scientific American Online caught up with Gates at this year's Consumer Electronics Show in Las Vegas, where he further detailed his thoughts on robotics in a Q&A session, podcast and video interview.

In May 2004 Scientific American's Gary Stix spoke with Gates about his interest in artificial intelligence and the need for ongoing research.

(Additional reporting by Adam Hadhazy)