Bill and Paul Allen had become mates when they were at Lakeside School. They had discovered their talents and become ambitious. As their talents were complementary it was imperative for them to stay together to gain success. So they did became the co-founders of Microsoft in 1976. Several times differences arose between the two partners on technical matters but the association continued.
During the period around 1980 Microsoft was growing fast. Bill realised that they needed the services of professionals who knew the fine points of trade, manufacture, marketing, finance and management. He hired an old Harward mate named Steve Balmer to help him in the business matters. Bill had appointed many old friends in his enterprise according to their qualifications. His theory was that old friends having sentimental involvement could work in better harmony. That is why he had appointed Steve as his business manager. Bill himself was a good manager.
Once there was an ugly confrontation between Steve Balmer and Paul Allen. Steve wanted to appoint 17 new people to take care of the fast expanding business of Microsoft Paul thought it would be sheer waste of money with little gain. It got so bad that Steve wanted to quit Microsoft. Bill intervened and mollified the frayed tempers. He reasoned with Allen and allowed Steve to hire the new staff as he had planned.
The differences of opinion is a normal thing. For years Bill and Allen had other professional disagreements but they stayed together.
Once Allen did bid farewell to Microsoft. The reason he gave was a congenital incurable disease he was suffering from. Bill acted like a true old mate and persuaded Allen not to leave the company. He did not want to lose his old friend. Allen had to give in. Bill included him in the Board of Directors of Microsoft. Inspite of being on his way to become the richest man of the world Bill did not grow any ego or behave arrogantly. He would not abandon his old friends. For him the sanctity of the friendship came first.
But in 2000 Allen departed inspite of the best efforts of Bill to retain him. This time Allen was firm and did not yield. It pained Bill. Allen had also stood by Bill like a true friend. He attributed the reason of his quitting to his disease and not to the differences.