A youngish man who looks like a graduate student sits on the door of his unpretentious dormlike room, spooning noodles from a plastic container. His glasses are smudged, his clothes are wrinkled, and his hair is tousled like a boy's. Yet this is an office, not a dorm room. And, while everyone calls the complex of 25 buildings a campus, it is not a college or university. It is the Microsoft headquarters in Redmond, Washington. And the person is no grad student. He is William H. Gates III chief executive and co-founder of Microsoft. Mr. Gates has changed the way we live through his first computing experience, the roots o