– Melinda Gates, co-chair of the Bill & Melinda Gates Foundation, explaining why she and her husband — who is no longer full-time at Microsoft — chose to tackle the world’s most intractable problems. These problems include U.S. education. Click here to watch a video highlight of my interview with Melinda Gates last week at the Fortune Most Powerful Women Summit. She and Bill initially were “naive,” she says, believing that if they invested in 10% of schools across the U.S., they’d make major strides in fixing education. Wrong. The Gates Foundation now puts its billions to work not just in schools but in education at the district, state and national levels. I profiled Melinda Gates in a Fortune cover story in January — her first-ever profile. Click here to read more about Melinda and Bill and their partner in giving away billions, Warren Buffett.