Who is Microsoft's biggest rival? Google? Guess again. Apple? Think different. Sony? None of these is the company that is still keeping Bill Gates & Co. on their toes, according to Microsoft's chairman. "The biggest company in the computer industry by far is IBM," said Gates in an interview with Reuters. "They have the four times the employees that I have, way more revenues than I have. IBM has always been our biggest competitor. The press just doesn't like to write about IBM."