"Trey didn't have a lot of confidence in social settings," says his father. "I remember him fretting for two weeks before asking a girl to the prom, then getting turned down. But Mary did. She was a star at social intercourse. She could walk into a room ..." He has the same toothy smile as his son, the same smudgy glasses covering twinkling eyes. But now, for just a moment, he is starting to tear up. His mind does not seem like a computer. He folds his arms across his stomach and starts to rock, gently.

He gets up to show some more pictures of Mary and of her mother. Both loved cards, and they would organize bridge games, as well as Password and trivia contests, after the big family dinners they held every Sunday. "The play was quite serious," Bill Sr. recalls. "Winning mattered."

As he wanders through the house, he points out more framed pictures of his son: Trey, the towheaded Cub Scout; Trey with sister Kristi, a year older, who now has the joy of being his tax accountant; and with Libby, nine years younger, who lives a few blocks away raising her two kids; with Bill Sr. and his new wife Mimi, the director of the Seattle Art Museum; and hugging his wife Melinda while listening to Willie Nelson play at their New Year's Day 1994 wedding in Hawaii.

"He's a busy guy," says Bill Sr., "so we don't see him a lot, but we spend holidays together." Thanksgiving was in Spokane, Washington, at Kristi's house, Christmas playing golf in Palm Springs, California, where Bill Sr. and Mimi have a place. They communicate mainly by E-mail. Just this morning he got one describing a photocopier Trey bought him for his birthday.

He lumbers over to a table where he has gathered some pictures of summer vacations they used to take with friends at a cluster of rental cabins known as Cheerio on the Hood Canal, about two hours away. There were nightly campfires, family skits and the type of organized competitive games the Gates family loved. "On Saturdays there was a tennis tournament, and on Sundays our Olympics, which were a mixture of games and other activities," Bill Sr. recalls. "Trey was more into the individual sports, such as water skiing, than the team ones."

In 1986, after Microsoft became successful, Gates built a four-house vacation compound dubbed Gateaway for his family. There his parents would help him replicate his summer activities on a grander scale for dozens of friends and co-workers in what became known as the Microgames. "There were always a couple of mental games as well as performances and regular games," says Bill Sr. as he flips through a scrapbook. These were no ordinary picnics: one digital version of charades, for example, had teams competing to send numerical messages using smoke-signal machines, in which the winners devised their own 4-bit binary code.

"We became concerned about him when he was ready for junior high," says his father. "He was so small and shy, in need of protection, and his interests were so very different from the typical sixth grader's." His intellectual drive and curiosity would not be satisfied in a big public school. So they decided to send him to an elite private school across town.

Walking across the rolling quad of the Lakeside School, Bill Sr. points out the chapel where his son played the lead in Peter Shaffer's Black Comedy. "He was very enthusiastic about acting. But what really entranced him was in there," he says, pointing to a New England-style steepled classroom building. With the proceeds from a rummage sale, the Mothers' Club had funded a clunky teletype computer terminal.

Learning BASIC language from a manual with his pal Paul Allen, Trey produced two programs in the eighth grade: one that converted a number in one mathematical base to a different base, and another (easier to explain) that played tic-tac-toe. Later, having read about Napoleon's military strategies, he devised a computer version of Risk, a board game he liked in which the goal is world domination.

Trey and Paul were soon spending their evenings at a local company that had bought a big computer and didn't have to pay for it until it was debugged. In exchange for computer time, the boys' job was to try (quite successfully) to find bugs that would crash it. "Trey got so into it," his father recalls, "that he would sneak out the basement door after we went to bed and spend most of the night there."

The combination of counseling and the computer helped transform him into a self-assured young businessman. By high school he and his friends had started a profitable company to analyze and graph traffic data for the city. "His confidence increased, and his sense of humor increased," his father says. "He became a great storyteller, who could mimic the voices of each person. And he made peace with his mother."