I worried that they would realize I was just a student in a dorm and hang up on me. Instead they said: "We're not quite ready, come see us in a month," which was a good thing, because we hadn't written the software yet.
From that moment, I worked day and night on this little extra credit project that marked the end of my college education and the beginning of a remarkable journey with Microsoft.
What I remember above all about Harvard was being in the midst of so much energy and intelligence. It could be exhilarating, intimidating, sometimes even discouraging, but always challenging. It was an amazing privilege - and though I left early, I was transformed by my years at Harvard, the friendships I made, and the ideas I worked on.
But taking a serious look back … I do have one big regret.
I left Harvard with no real awareness of the awful inequities in the world - the appalling disparities of health, and wealth, and opportunity that condemn millions of people to lives of despair.
I learned a lot here at Harvard about new ideas in economics and politics. I got great exposure to the advances being made in the sciences.
But humanity's greatest advances are not in its discoveries - but in how those discoveries are applied to reduce inequity. Whether through democracy, strong public education, quality health care, or broad economic opportunity - reducing inequity is the highest human achievement.
I left campus knowing little about the millions of young people cheated out of educational opportunities here in this country. And I knew nothing about the millions of people living in unspeakable poverty and disease in developing countries.
It took me decades to find out.
You graduates came to Harvard at a different time. You know more about the world's inequities than the classes that came before. In your years here, I hope you've had a chance to think about how - in this age of accelerating technology - we can finally take on these inequities, and we can solve them.