In a strongly-worded ruling, a Seattle court has denied a request by Microsoft to block a California software company from calling itself Lindows.com and its Linux-based operating system, LindowsOS.

Lindows is a version of Linux that its maker claims can run both Linux and Windows programs.

Judge John Coughenour found Microsoft has raised serious questions about the validity of its trademark Windows. The ruling denied Microsoft's request for a preliminary injunction in the case but does not stop the software giant from seeking a trial on the issue.

"Although Lindows.com certainly made a conscious decision to play with fire by choosing a product and company name that differs by only one letter from the world's leading computer software program," Coughenour wrote, "one could just as easily conclude that in 1983 Microsoft made an equally risky decision to name its product after a term commonly used in the trade to indicate the windowing capability of a graphical user interface."

The judge also said Microsoft has not stopped literally hundreds of other trademarks and products from using all or a portion of 'windows' in their names.

Microsoft had argued that the close similarity in the Lindows and Windows names would confuse customers and dilute its trademark for Windows products. The company sued Lindows over its name in December.

In a statement, Microsoft said: "We are disappointed with the ruling, but we intend to pursue our claim to protect our trademark."

Meanwhile, Lindows.com chief executive Michael Robertson said: "We're obviously satisfied with the court's ruling. Our hope is that we can move beyond the courtroom and focus on our goal of bringing choice back to the PC business."

He said the company hopes to roll out its products "without further impedance".

Lindows takes its name from combining 'Linux' and 'Windows' and its website contains the following disclaimer:

"LindowsOS is a trademark of Lindows.com, Inc. Linux© is a registered trademark of Linus Torvalds. Microsoft© Windows© operating system is a registered trademark or service mark of the Microsoft Corporation."