Microsoft started the war against Linux at least as far back as 1996. It has been going on for 15 years or more:

http://groups.google.com/group/comp.os.linux.advocacy/msg/67a9771825742ab0

Microsoft doesn't even deny any of the tactics below. In fact, they have defended these activities in court hearings and commission hearings as "typical of the PC industry", because they control the PC industry.