Office romance: how Bill met Melinda

In summer 1986, freshly graduated from Duke University with a degree in computer science and economics, Melinda Ann French was working as an intern for IBM. She told a recruiter she had one more interview – with a new company called Microsoft. The recruiter was keen. "If you get a job offer from them," she said, "take it, because the chance for advancement there is terrific."

Indeed. Six-and-a-half years later, Melinda Ann had advanced through the company, from software marketing tyro to general manager of information products such as Expedia and Encarta; more significantly, she had advanced to a senior role in the heart of the chief executive, Bill Gates, soon to become the world's richest man. Today, she is one half of the world's top charity foundation, with personal jurisdiction over the spending of $80bn (£40bn). Clever, raven-haired, strong-featured and tough as nails, she brings equal amounts of compassion, common sense and business nous to the small matter of alleviating world sickness and poverty.

Born in 1964, she grew up in Dallas, Texas, the daughter of Ray French, an engineer and house-rentals agent. At school, Melinda was earnest, driven and goal-orientated. Her introduction to the cyber-world came at 14, when her father brought home an Apple II, one of the first consumer computers available. She was soon playing computer games, and learning the Basic programming language.

It has always amused Bill Gates that his wife is better educated than him – he is America's most famous college drop-out. They met in 1987, four months into her job at Microsoft, when they sat next to each other at an Expo trade-fair dinner in New York. "He was funnier than I expected him to be," she reported, neutrally. Months went by before, meeting her in the Microsoft car park, he asked her out – in two weeks' time. She said, "ask me nearer the time." He had to explain to her the ceaseless daily flood of meetings.

Whatever first attracted Ms French to Bill Gates, he was struck by her forthrightness and independence. It was she who first spurred him into impulses of charity. After their engagement in 1993, during Melinda's "wedding shower", her mother Mary, suffering from breast cancer, read her an admonitory letter whose gist was, "from those to whom much is given, much is expected". Mary died months later, but her advice provoked the William H Gates Foundation. Run by Bill's father, its aim was to put laptops in every classroom. Then the couple decided that the most pressing issue in the US was reforming the education system.

Then, after their wedding in Hawaii (on New Year's Day 1994) Melinda read in The New York Times about the millions of children in developing countries dying of malaria and TB. She made world poverty their priority concern.

Melinda now spends 30 hours a week on foundation work, as she and Bill assess the charity presentations that flood in. Of the 6,000 requests the foundation receives each year, they read only the ones asking for $40m or more. "We go down the chart of the greatest inequities, and give where we can effect the greatest change," she told Forbes magazine, in a tone that suggests she doesn't regard it as rocket science. The foundation also links up with other charities and companies like Glaxo on more ambitious projects – like the Global Alliance for Vaccines and Immunisations, which kicked off with donations of $1.5m from each of 17 governments.

It's hard to keep sight of the woman behind the world's top charity: the high-achieving schoolgirl who loved complicated jigsaws and once scaled the 14,000ft Mount Rainier with ropes and crampons; the mother of three; and the devout Catholic who visited Calcutta to talk to Aids sufferers in Mother Teresa's Home for the Dying. But it's clear that the Foundation needs her clarity and good sense. Time magazine, when it put Bill Gates and Bono on the cover as "Person[s] of the Year," included Melinda Gates because she is the heart, as well as the brains, of the organisation. "Lots of people like Bill – and I include myself – are enraged," said Bono, "and we sweep ourselves into a fury at the wanton loss of lives. We need a much slower pulse to help us to be rational. Melinda is that pulse."