The complaint filed by Los Angeles resident Emma Alvarado last week accused Microsoft of breaking California's unfair business practice and restraint of trade laws by requiring customers to purchase a copy of Windows Vista or Windows 7 if they want to downgrade to the older Windows XP.

Alvarado's lawsuit asked a California federal judge to grant the case class-action status, which would let others join her in suing Microsoft.

In 2009, over the same downgrade rights, claiming that the company used its position as the dominant operating system maker to "require consumers to purchase computers pre-installed with the Vista operating system and to pay additional sums to 'downgrade' to the Windows XP operating system."

That in February 2010 by a Washington federal judge who said Alvarado had not proved Microsoft benefited from the downgrade practices.

"Downgrade" describes the Windows licensing rights that Microsoft gives users, who are allowed under some circumstances to replace newer versions of Windows with an older edition without having to pay for another license. In effect, the license for the newer Windows is transferred to the older edition.