It was in 1975 that Gates launched the company that would become the biggest name in computer software. His exit has many wondering what the 52-year-old billionaire will do with his time.
The computer impresario, who revolutionized how the world uses PCs, says he's looking forward to having more time to oversee his $38 billion foundation.
The third-richest man in the world's send-off will include a star-studded video that spoofs his last day.
Actor Matthew McConaughey -- who's been caught shirtless more than once by the paparazzi -- appears in the video coaching the software mogul through a workout at the gym.
"That's good work you want to keep going?" McConaughey asks Gates.
"Am I ready to take my shirt off yet?" Gates jokes.
Democratic presidential candidate Barack Obama also got in on the action, confusing Gates with another famous Bill.
"Hey, it's Bill," Gates says into a phone.
"Bill Shatner, from Star Trek?" the Illinois senator asks.
Countless celebrities and politicians, including Jon Stewart and Al Gore, all try to help Gates fill his new-found spare time.
As co-founder of Microsoft, Gates has become one of the few "rock stars" in the tech world. He's come a long way from being a Harvard dropout who was once arrested for a traffic violation in 1977.
After building the company in the 1980s, Microsoft's operating systems are now on the vast majority of computers; some estimates put the number as high as 90 percent.
"He's built a company that is by any measure the most powerful technology company in the world today," said Rob Enderle, a technology industry analyst.
While Gates will step down Friday as chief software architect, his duties will be filled by three senior Microsoft staffers. Although he'll remain chairman of the board, he'll still be missed, Enderle said.
"Its hard to find a single person or any group of people that can embody both the authority and the vision that Bill Gates had," the analyst said.
As for his new found free time, whether it's philanthropic work in Africa, playing bridge with Warren Buffett, or exploring his more creative side, Bill Gates will surely have the time -- and money -- to do just about whatever he wants.