Microsoft filed counterclaims against 20 US states on Tuesday evening and issued a strong legal rebuttal of charges of monopolistic practices made against it by the states' attorneys-general and the Department of Justice in May.

In its first formal response to the landmark lawsuits, Microsoft said they were "completely groundless" and the states' actions in particular "unconstitutionally undermine the company's intellectual property rights."

Papers filed in the US District Court in Washington DC, to meet a deadline of six weeks before the hearing of the actual case, maintained that:

• Microsoft planned to integrate its Internet Explorer browser into the Windows operating system long before its rival Netscape even existed. It says there was already consumer demand for Internet enabled operating systems as far back as 1993 when it began working on the project. The Justice Department says the integration was intended to put Netscape out of business.
• Explorer is gaining popularity with consumers not because of an unfair advantage but because of its "superior technology" compared to the Netscape Navigator browser.
• Microsoft had not tried to "illegally divide the browser market" with Netscape in talks in 1995
• The company did not, as the government alleged, enter into exclusionary contracts with Internet service and content providers. It allowed them to "promote Internet Explorer in parity with their promotion of other web browsing software."
• It also did not restrict the ability of computer manufacturers to alter the Windows desktop screen that users see when they first boot their computers, contrary to the government's claims.

With regard to the counterclaim against the 20 states, Microsoft says copyright owners have the right to license their products to third parties in an unaltered form. The states were trying to infringe that right.

The company promised a far more detailed response in time for the next filing deadline of August 10.

Judge wants 30-day hearing

The presiding judge, Thomas Penfield Jackson, has said he wants the actual hearing to last no more than a month, although appeals could drag on for years in what is seen as an historic court case.

Microsoft intends to further argue that every other major developer of operating systems has included Internet support.

It has already subpoenaed Novell, Sun Microsystems, IBM, Apple, Caldera, Network Computer and Santa Cruz Operation to support its case

The Justice Department is reported to be focusing on proving that Internet Explorer's integration along with exclusionary contracts with Internet service providers was aimed at protecting its Windows operating system from rivals such as Netscape.