Abstract: Microsoft has brilliantly exploited its current control of the personal computer operating system (OS) market to grant itself advantages towards controlling tomorrow's operating system market as well. This is made possible by the control Microsoft has asserted over user "defaults," a power Microsoft possesses thanks to a combination of (1) Windows' high market share, (2) the "network effects" that make switching to an alternative so difficult for any given consumer or computer manufacturer, and (3) software copyright, which largely prevents competitors from generating software that defeats network effects. The author suggests a much-reduced term of copyright for computer software--from 95 years to around five years--as a means of preventing antitrust problems before they arise.