(FORTUNE Magazine) – Larry Ellison personally endorses his products. Carly Fiorina and Sam Palmisano wish he'd quit working so hard. In the 19 years since Dell, 38, founded Dell Computer in his University of Texas dorm room, he has exploited the Net and just-in-time manufacturing to fundamentally reshape a commodity business. He has proved that anything his competitors can do, he can do cheaper. Dell--whose net worth is estimated at more than $17 billion, making him by far the richest self-made American under 40--sells more PCs and workstations than anyone else. No wonder his methods are studied across industries and around the world. --Noshua Watson