Microsoft Co-Founder is a term used to describe two individuals, Bill GATES and Paul ALLEN, who co-founded the Microsoft Corporation in 1975. Bill GATES is an American business magnate, investor, author, philanthropist, and humanitarian. He is best known as the principal founder of Microsoft Corporation. Paul ALLEN was an American business magnate, investor, and philanthropist. He co-founded Microsoft with Bill GATES in 1975. Together, they revolutionized the computer industry and changed the way people use technology.