Robert D. Novak's Sept. 23 column ["Vendetta Against Microsoft"] contains false charges leaving the impression the Justice Department brought the Microsoft case for some reason other than the legal merits. That's simply not true.

We prosecuted Microsoft to thwart anticompetitive activity that limited innovation and consumer choice in one of the few high-tech markets where consumers now lack real choice: operating systems for personal computers. At the recent trial, we put on a mountain of evidence establishing that Microsoft's Windows has long had a monopoly in this important, multibillion-dollar market, and the firm repeatedly used its monopoly power to stifle new technologies that threatened to permit competition to emerge.

Microsoft's monopoly has endured because the huge number of applications that run only on Windows makes it virtually impossible for another operating system to compete effectively. New "middleware" technologies, most notably Netscape's browser and Sun's Java, offered the prospect that computer programs would not have to be written for a specific operating system, and computer users, no longer dependent on Windows, could choose among different operating systems, leading to lower prices and better products.

As the evidence demonstrated, Microsoft used a wide variety of anticompetitive means to prevent the middleware threat from taking hold. It tried to divide markets. It insisted on exclusionary contracts that impeded competitors from getting their products to consumers. It prevented computer manufacturers from featuring non-Microsoft products and forced anyone licensing Windows to install Microsoft's browser. It even absorbed huge losses so no one else could effectively compete in the browser market.

By crushing this threat to its monopoly, Microsoft kept consumers from having a meaningful choice of operating systems for their PCs. Because of this lack of competition, consumers also pay more for Windows now than they did five years ago, even as the price of personal computers has fallen dramatically.

In short, this case was brought solely on the basis of the facts and the law. There was no other motive -- political or otherwise -- that affected our decision. Novak's innuendo notwithstanding, the White House had absolutely no involvement.

The support that Novak cites for his "vendetta" thesis -- i.e., that we encouraged foreign antitrust authorities to bring charges against Microsoft -- is as baseless as the thesis itself. Had Novak checked with me, he would have found that the meetings referred to in his column were part of routine efforts by antitrust division personnel to meet with our foreign counterparts to discuss antitrust policy and boost cooperation in international antitrust law enforcement efforts. (Indeed, those efforts have contributed to successful prosecutions that resulted in criminal fines in excess of $1 billion this fiscal year against participants in international price-fixing cartels.)

As we advised the Senate in July 1998, no Division personnel in those meetings ever divulged confidential information to any foreign government or encouraged one to take or threaten legal action against Microsoft. In fact, not only have we never encouraged other governments to bring suit against Microsoft, we have ourselves declined to proceed against Microsoft in other instances, despite complaints by third parties urging us to take action.

With regard to Novak's reference to the comments attributed to David Boies by The Guardian, the article apparently arose from a brief telephone conversation that he had with a reporter while Boies was in Jacksonville, Fla. (not in London, as Novak reported). Boies was asked to describe the legal rules in the United States regarding antitrust claims by non-U.S. citizens and he did. But he never expressed an opinion as to whether any private party (American or otherwise) had a claim against Microsoft, nor did he solicit or encourage any party to assert such a claim, or consult counsel regarding such a claim.

Novak's charge that he did is false. And Boies is well aware that by virtue of his representation of the United States in its suit against Microsoft, he is barred from representing any other party, including private plaintiffs seeking damages, in any related matter.

The Microsoft case is of great importance to the future of innovation and competition, and we welcome the opportunity to see its merits debated in any responsible forum. But that's a far cry from falsely impugning the motives or conduct of the Department of Justice in seeking to enforce the law.

The writer, an assistant attorney general, heads the Justice Department's antitrust division.