Microsoft has gone back to court to contest an earlier decision allowing operating system manufacturer Lindows.com to continue trading with a name that closely resembles the software giant's own Windows product.

Microsoft has asked US District Judge John Coughenour to overturn his decision of 15 March when he threw out its argument that Lindows.com, a company that uses both Windows and Linux, was deliberately confusing customers.

Judge Coughenour said that he even doubted whether Windows was entitled to brand protection, as the US Patent and Trademark Office has denied it exclusivity on several occasions.

He wrote at the time: "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, 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."

Now Microsoft is back, arguing that the court was wrong to focus on an operating system feature rather than the operating system itself.

The case will hinge on whether the term Windows is generic or descriptive, and will again seek to prevent Lindows.com using its name.

Microsoft has claimed that the court made a "fundamental misapprehension of the test for 'genericness'" when it concluded that Windows not protected by trademark descriptions.