In 1997, Gates and Microsoft invested $150 million in Apple. He also developed and shipped versions of Microsoft Office, Internet Explorer, and development tools for Macintosh. Gates and Jobs made the announcement via satellite link at the Macworld Trade Show in Boston, Massachusetts.
More than 8 million customers of Mac were using Microsoft Office on their Mac computers. It was a move meant to boost Apple popularity while making Gates and Microsoft a load of cash. Additionally, the move was done to keep anti-trust lawyers off Microsoft's back.
It seems like a lot of money to give to Apple, but Microsoft spent $450 million alone that year on WebTV. The companies both agreed to work together on Java programming language and other programming language to be user friendly and consistent with both companies.
The investment news along with Jobs stating they would be getting new board members pushed the company’s stock up more than 40%. The $150 million investment was to be used in its core markets of education and creative content. They hoped to gain a higher percentage of its revenue from software and services from these core markets.