Bill Gates' original business partner was Paul Allen. Although Gates and Allen originally co-founded Microsoft, Allen has since left the company and has been pursuing other research, business and philanthropic endeavors as an investor and entrepreneur.
Gates and Allen had known each other since middle school. They both attended Lakeside High School in Seattle, Wash., and became friends who would later attend Harvard University together. Gates and Allen started a software firm together, and although Allen anticipated that their partnership would have a 50-50 proposition, he eventually agreed to a 64-36 split in Gates' favor. This set the precedent for the arguments and issues the co-founders would face in the future, which Allen has since made public.