Bill Gates proves to be an astute media critic in a nearly 40-minute television interview about his philanthropic activities, which will be broadcast this Friday on Now with Bill Moyers. Asked by Moyers what drew him to world health issues, the Microsoft mogul replies that it was a report, issued 10 years ago, showing that more than a half-million children die every year of rotavirus, which causes diarrhea in infants and children.

"And I said to myself, ‘That can’t be true,’" Gates recalls. "You know, after all, the newspaper — whenever there’s a plane crashing and 100 people die, they always report that. How can it be that this disease, which is killing a half-million a year, I’ve never seen an article about it until now.... And so I thought, ‘This is bizarre. Why isn’t it being covered?’ There’s a mother and a father behind every one of those deaths that are dealing with that tragedy."

Gates and Moyers appear in front of a live audience of mostly young people at Columbia University’s Mailman School of Public Health. It is an ideal image-burnishing opportunity for Gates, whose best-known public appearances before this were those God-awful, evasive videotapes of his testimony in the Microsoft antitrust trial. But this is no mere exercise in public relations. Gates has made a commitment to give away nearly his entire fortune, currently estimated to be around $40 billion, through the Bill and Melinda Gates Foundation. And he is focusing on the most tragic, intractable problems that the Third World faces — AIDS, malaria, even an obscure disease called trachoma, a leading cause of blindness in poor countries.

Now 47, Gates still appears unusually boyish. Dressed in a blue, open-collared shirt and dark pants, his hair only slightly less disheveled than it used to be and his blue eyes animated behind reasonably stylish wire-rimmed glasses, Gates speaks excitedly about his new life as a philanthropist, his voice cracking in the upper register as though he were an adolescent whose voice is changing. (Disclosure: I own a piddling number of Microsoft shares.)

Perhaps the most fascinating aspect of the interview is that Gates comes across as anything but the successful entrepreneur who thinks he can apply the lessons he learned in business. Indeed, at one point he tells Moyers that one particularly horrifying statistic — that 11 million children die every year from preventable diseases — is "a failure of capitalism." He adds: "You know, capitalism is this wonderful thing that motivates people, it causes wonderful inventions to be done. But in this area of diseases of the world-at-large, it’s really let us down."

Showing a diplomatic side that’s rarely been on display in the past, Gates parries a question from Moyers about "the Bush administration’s retreat from women’s health issues, reproductive rights around the world" not by criticizing the president, but by urging "the citizenry" to "speak up enough and make it a big issue."

All in all, it is a bravura performance by a man who once symbolized the inward, wealth-driven values of the New Economy. And if Microsoft isn’t quite the high flier that it used to be, it’s still in far better shape than the vast majority of the dot-coms whose glory it once shared. That’s good for Gates, of course, but it turns out that it’s good for the world, too.

The Gates interview will be broadcast this Friday, May 9, at 9 p.m. as part of Now with Bill Moyers, on WGBH-TV (Channel 2). For more information, go to www.pbs.org/now/science/gates.html.