Some people don't take well to retirement. Two years after leaving AST Research, the computer manufacturer he cofounded, Thomas Yuen is working on not one but six new California high-tech start-ups. Yuen says he's taking an active role in most of the start-ups; he's organizing four of them to operate out of the same building, for example. His latest investment? Nine-month-old NuReality, of Santa Ana, Calif., the maker of a sound-enhancement system for video games and multimedia. Yuen says the multiple responsibilities involved in helping grow AST from a small garage outfit to a Fortune 500 company gave him "on-the-job training" for working with six companies at once. "I didn't think I'd do so many [new companies]," he says. "I just couldn't hold back my enthusiasm. I'm an engineer by training and always have a yearning for leading-edge technologies."

To keep up, Yuen uses every spare minute -- including the 15 hours a week he spends on dialysis treatment. "If you are able to screen out the pain and inconvenience, you can train yourself to do useful tasks," says the 42-year-old, who was diagnosed with end-stage renal disease 13 years ago. Three nights a week (so as not to interfere with business hours) Yuen receives dialysis in his home at a station equipped with a desk, a phone, and a computer. How does he view the time? As an opportunity to think about the computer industry. -- Alessandra Bianchi