Microsoft said today that the government has failed to show that the company broke the law, illegally tied its browser to the Windows operating system or monopolized the operating-system market, according to a legal brief filed in US District Court.

The company also rejected the government's and a judge's claims that Microsoft has a monopoly in operating systems. "Having an extremely popular product does not make a company a monopolist," Microsoft argued in its brief.

The brief is the company's rebuttal to the government's filing last month that Microsoft violated key provisions of U.S. antitrust laws. It comes as both sides have been meeting in Chicago with a mediator to explore a possible settlement.

Denied Not surprisingly, Microsoft's legal argument disputes every legal claim made by the government in its earlier brief.

Specifically, Microsoft said the government failed to show any of the necessary elements needed to make its claim that the company tried to crush Netscape Communications.

The browser and the operating system are a single product, Microsoft argued, and antitrust laws do "not contemplate judicial dissection of that product into parts and reconstitution of these parts".

No evidence On the charge that Microsoft prevented browser competition through its contracts with content providers, online services and others, the company argued that the government failed to show these agreements prevented Netscape's access "to more than 40 per cent of the purported market for Web-browsing software."

The 40 per cent figures comes from a 1998 ruling, where trial Judge Thomas Penfield Jackson said that the government must prove Microsoft was blocked from at least that amount of the market in order to prevail on "exclusive dealing" claims.

Microsoft said that Netscape distributed more than 160 million copies of its Web-browsing software in 1998 alone.

Microsoft also defended its right to impose first-screen restrictions on PC makers as allowed under copyright laws, which require manufacturers to present specific start-up screens on computers they sell with Windows.

Both sides are due in court on February 22 to make their final legal arguments.