AOL Time Warner filed an antitrust lawsuit against Microsoft in federal court Tuesday, seeking damages for violations of antitrust law found in a landmark government case against the software giant.

The seven-count lawsuit, filed in U.S. District Court for the District of Columbia, said the once-dominant Netscape browser suffered harm through Microsoft's unfair promotion of its own Internet Explorer browser.

AOL, which now owns Netscape, wants Microsoft to cease its contested business practices and pay damages. Microsoft's Internet Explorer now dominates the browser market.

A U.S. appeals court in June upheld findings in the U.S. Justice Department's suit against Microsoft that the company illegally used its monopoly in personal computer operating systems to maintain its dominance.

The Justice Department and nine states joining that case have reached a proposed settlement. Nine other states are seeking stiffer penalties against the software giant.

Microsoft bundled the Internet Explorer browser with its operating system, leading to the government's suit.

The Justice Department and states had argued at trial that Microsoft feared Netscape's popular browser could evolve into a computer platform that could rival Microsoft's Windows operating system.

AOL executive John Buckley noted the court ruling and said, "This action is an attempt to get justice in this matter."

The company also asked for an immediate injunction against "ongoing and further damage" involving Netscape's browser, Buckley said.

One possible option, if a judge rules in favor of AOL, would be to force Microsoft to sell a stripped-down version of its Windows operating system so computer manufacturers could choose which Internet browser to offer. That has also been requested by nine state attorneys general suing Microsoft in federal court.

University of Baltimore law professor Bob Lande said of AOL and its lawsuit: "This is a company that obviously can afford it, and wouldn't take the step lightly."

"I think they've got an excellent chance of success given that the government has established the facts and established that Microsoft has broken the law," he said.

A judge would still have the challenge of choosing a remedy that would restore competition to the Internet browser market. Netscape has only a sliver of the Internet browser market, compared to its dominance several years ago.

"You can't literally put the market back in the competitive position it was in, so you'd have to think of a forward-looking remedy to help restore competition in the market as best as possible," Lande said.

Reuters and the Associated Press contributed to this report.