Gates attended Harvard for two years and then left to start Microsoft.
Bill Gates attended Harvard University from 1973-1975. He was studying law, because he intended to be a lawyer like his father. Yet Gates was more interested in the fledgling computer industry than in law.
In college, Bill Gates and his friend Paul Allen contacted the MITS computer manufacturer explaining that they had a new language for the personal computer. MITS was interested. In four weeks, they were able to demonstrate the new programming language without a hitch.
Gates left Harvard to start the company Microsoft April 4, 1975.
Gates ... believed that there was a market for computer software and that the market was going to expand rapidly.... (eNotes)
The company had a difficult time getting off the ground at first. The software was pirated by hackers, and the company was not making enough money to pay the bills. Gates responded with the famous 1976 “An Open Letter to Hobbyists” to remind people that someone wrote that software they were using.
Two surprising things are apparent, however, 1) Most of these "users" never bought BASIC …and 2) The amount of royalties we have received from sales to hobbyists makes the time spent on Altair BASIC worth less than $2 an hour. (William Henry Gates III, "An Open Letter to Hobbyists")
In the end, Microsoft was enormously successful. Gates was not the first or the last successful person to leave college to pursue his dreams, but he is one of the most fascinating.