Although Joel Klein, the assistant attorney general in charge of the Justice Department's antitrust division, characterized Microsoft's activities as ''illegal,'' he said the government was not leveling a criminal investigation. This is a highly competitive marketplace. Microsoft's position is certainly powerful. Dan Kusnetzky, director of operating-systems research for International Data Corp., a research firm in Framingham, Massachusetts, said that based on 1997 shipments of operating systems, Microsoft's Windows and DOS programs accounted for about 84.5 percent of the units shipped. Mr. Kusnetzky said.
Servers are central computers that are linked to individual client machines.
In an office network, each employee's desktop computer would be a client. In the server market, Mr. Kusnetzky said, Microsoft had about a 37 percent market share, followed by Novell Inc.'s NetWare operating system, with about 27.5 percent. He said that market share itself was not the sole determinant of whether a monopoly existed. If a company could not raise prices at will or exclude competition, he said, then it could not be shown to have monopoly power. ''Even if you have monopoly power,'' he said, ''you have to be shown to have used it in an exclusionary or predatory way'' for the antitrust rules to apply. If there is a legitimate business justification for an action, he added, even if it also has predatory effects, the activity is not illegal.