Microsoft Corp has been hit with more class action lawsuits, this time in Ohio and Florida, where the software giant has been yet again charged with abusing its monopoly power to overcharge customers for Windows operating system upgrades.

The news follows hot on the heels of an almost identical class action suit filed on Monday in the Superior Court of San Francisco. The cases are drawing on evidence from Microsoft’s antitrust case in Washington where earlier this month Judge Jackson found that Microsoft was a monopoly and accused the giant of using that power to squash competition and harm consumers.

The two Ohio suits, filed by attorney Stanley Chesley, were entered in the US District Court in Columbus and in the state court of Cincinnati. Chesney told ComputerWire that estimates put collective consumer damages to around $10bn. He added that a victory in the district court in Columbus alone could triple that figure, while the state court suit could double it, he said.

The 20-page district court filing said Microsoft’s actions For at least the past four years….have caused plaintiffs to pay monopoly prices for their operating systems….have also caused Plaintiffs to incur costs necessary to remove an unwanted browser application called Microsoft Internet Explorer, or suffer the performance degradation resulting from its undesired presence along with the operating system.

Similarly, Microsoft has used its monopoly power to charge illegal monopoly prices, states the Florida suit. Filed by law firm Haggard & Parks PA in Miami-Dade County judicial court, it accuses Microsoft of violating both federal antitrust laws and the Florida Deceptive and Unfair Trade Practices Act.

Like the San Francisco filing, the plaintiffs of these latest cases are demanding compensatory damages. According to other reports more suits are soon to follow including one more from consumers in California and another from in the State of Georgia.