Mark Zuckerberg's dentist dad was an early adopter of digital x-rays. Jack Welch blew the roof off a factory. Carol Bartz was a Wisconsin farm girl who got into computers. No two C.E.O.'s have the same origin story — so we tell them all! How the leaders of Facebook, G.E., Yahoo!, PepsiCo, Microsoft, Virgin, the Carlyle Group, Reddit, and Bridgewater Associates made it to the top. (Part 2 of a special series, "The Secret Life of C.E.O.'s.")