Okay I will give another try. Elon was doing PhD and discontinued while he founded his first company in 90's. Since computers was not his main interest he used windows to the get the work done because windows is easier to learn and start getting output. From then on elon was crazy busy to do lot of other things and never got time to learn Linux . At the same time Elon wants control over everything which means at any point in time he wants to understand what the software is doing and even be involved in making changes to it if required first hand. Now with this background obviously Elon went with windows because he don't have to learn Linux and can use his already learnt windows knowledge.