That was the cause of some confusion last year, when Dell Inc. was accused of to downgrade a new computer to XP. Dell, however, countered that although it did charge $20 to install XP on the machine, as well as to cover the cost of the additional media, the bulk -- $120 of the $150 -- was the price of upgrading the PC from the standard Home Premium to the more expensive Business edition.

Microsoft does not offer downgrade rights with its Vista Home Premium, the most popular of Vista's editions.

"Microsoft mandates that customers who want to downgrade to XP must purchase the license to Vista Business or Vista Ultimate," said Dell spokesman David Frink last December. "[That's] typically about a $130 premium, though some retail outlets charge more."

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. The practice became popular last year when users, unhappy with Vista's performance on the new PCs they bought, instead sought ways to run the leaner XP.

The lawsuit, filed by Los Angeles resident , charged Microsoft with multiple violations of Washington state's unfair business practices and consumer protection laws through its policy of barring computer makers from continuing to offer XP on new PCs after Vista's early-2007 launch. She claimed Microsoft's practice resulted in customers paying more for XP than they otherwise would. "They have been forced to pay substantially more to acquire the Windows XP operating system than they would have to pay in a competitive marketplace," the suit said.