Abstract: A method of suppressing unwanted windows created by an operating system is described. The method comprises: monitoring calls from the operating system relating to creation of a window and ascertaining if a monitored call relates to creation of a window of a type corresponding to a window type to be blocked. If the window is not of a type that is to be blocked, then the method involves displaying the window. If the window is of a type that is to be blocked, then the method involves: registering a new window procedure for that window; and returning an error message to the operating system using the new window procedure to suppress display of the window.