James H. "Jim" Clark, the founder of two extraordinarily successful Silicon Valley computer software companies, is a classic example of a visionary entrepreneur. While still a professor at Stanford University in 1981, he founded Silicon Graphics, today a billion-dollar computer workstation company. In December 1994, Clark cofounded the revolutionary Netscape, which immediately became the Internet's dominant online browser. In September 1997, he was listed 15th among Forbes's "Technology's Richest 100" with an estimated wealth of $597 million.

A native of Texas, Clark showed little academic promise as a child. He grew up in a single-parent home with few financial resources. He acted out in school, once even exploding a bomb on a school bus, and was finally expelled after telling a teacher to go to hell. When he joined the Navy, Clark again found himself at odds with authority: he marked every question "yes" on a multiple-choice exam, since each one seemed...