He was a freshman at Harvard University in 1973. He left Harvard to make software. Bill Gates saw an opportunity to transform the personal computer, which was expensive and difficult to use. He decided that computers could be made less expensive and easier to use. Gates started Microsoft in 1975 with Paul Allen in the city of Albuquerque, New Mexico. Gates then went on to develop the Windows operating system, which at first wasn't well received but with time became the most used operating system in the world.