"We are currently witnessing unprecedented rates of change in technology and audience expectations," said Mark Thompson, BBC director-general.
"To ensure that the BBC is able to embrace the creative challenges of the digital future, we need to forge strategic partnerships with technology companies and distributors for the benefit of licence payers."
The memo sets the terms under which the organisations can explore new opportunities for delivering and consuming BBC digital content.
Mr Thompson and Ashley Highfield, director of New Media, met Bill Gates in Seattle yesterday to sign the non-exclusive agreement and discuss the BBC's digital strategy.
This includes a radical re-invention of the BBC website to incorporate web 2.0 internet-based services and new ways to share and archive online content in the future.
"Microsoft's strength is in driving digital innovation, and our vision is to open up rich, new consumer experiences that allow people to enjoy digital content anytime, anywhere and on any device," Gates said.
"This vision fits squarely with the BBC's charter to lead the industry in delivering content that is compelling and accessible. I'm delighted that we're taking this important step, and I look forward to working together to develop new models for content delivery and consumption."
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