Most of the end users who have just say 5% knowledge of computers are comfertable with windows as the GUI of windows is very user friendly.The day Linux or for that instance any other Operating system makes its GUI as user friendly as Windows the craze of Windows is going to reduce. Maximum High end users like any servers prefer using Linux as it is an open sourse and can be modified as per your requirement and also it is much more secure than windows with it's IP tables. Moreover Windows is mostly effected by piracy then any other OS!