Microsoft chairman Bill Gates formally entered the computer business in 1975 as a gangly geek and later this month will semi-exit as an industry luminary leaving behind a billion-dollar juggernaut and a legacy of software, personal computing, innovation, and tough and sometimes unfair competition.

For more on Bill Gates legacy see:
Bill Gates in pictures: A retrospective
Bill Gates: the video tribute
Mitchell Ashley: Gates; Ruthless, Dominance and Respect
Ron Barrett: Interesting thoughts about the legacy of Bill Gates

Gates, who will remain as Microsoft chairman while devoting most of his time to working with the Bill & Melinda Gates Foundation, is synonymous with Windows and the monumental impact it and other software made in delivering computing to the masses.

Competitors, colleagues and industry observers point to Gates' intellect and passion that pushed an industry from infancy to maturity, but also revealed an arrogance and competitive spirit that at times had little tolerance for other winners, such as Novell, Netscape, open source and Google.

And along the way there were famous stumbles followed by famous recoveries, such as Gates' 1995 "Internet Tidal Wave" memo that declared the Internet was "the most important single development" since the IBM PC at a time when Silicon Valley was already well across that bridge.

"One of the things that is interesting about Gates is the extent to which he stamped his own personality on the organizational culture of Microsoft and by extension on a great deal of the personal computing industry," says Thomas Haigh, a historian of computing at the University of Wisconsin at Milwaukee. Haigh says Gates was a combination of a techie and a businessman who really wanted to get software out the door, win market share and beat the competition.

Click to see: A timeline of Bill Gates

"Putting those two things together made him distinctive among his generation of software industry leaders and explains a lot about how Microsoft developed as a company," Haigh says.

After 33 years in the business, the Microsoft co-founder is both revered and reviled.

"There are not too many people who can be Darth Vader and Luke Skywalker at the same time," says Dana Gardner, principal analyst for Interarbor Solutions, who has spent more than a decade following Microsoft and the high-tech industry. "To a lot of people he was the evil empire. He stifled innovation and creativity. He was aggressive in business. Not just aggressive, but hyper aggressive, and that did not serve Microsoft well over time."