There was also the plethora of undocumented Windows API's the Office programs were using that weren't available to anybody else. That was one of the thrusts of the antitrust lawsuit leveled against Microsoft. The best thing coming out of that was Microsoft's $150 million investment into Apple in an attempt to convince the government that they had competition and weren't a monopoly. Apple had 2% of the marketshare at the time - some competitor!