For Microsoft's legal department, as Yogi Berra once said, it must seem "like déjà vu all over again."

The Redmond software giant is already enmeshed in a class-action suit over whether it mislead people who purchased PCs prior to the launch of Windows Vista -- the so-called "Vista Capable" suit.

Microsoft's (NASDAQ: MSFT) lawyers are also dealing with recent European Commission rulings against it for anticompetitive practices, including illegally tying Internet Explorer (IE) to Windows.

Now, the company is under antitrust attack again, this time for the fees PC vendors charge to consumers who buy PCs preinstalled with Vista and then "downgrade" to Windows XP.

The suit, which also requests class-action certification, was filed Wednesday by Emma Alvarado of Los Angeles County in federal district court in Seattle. Alvarado claims that she bought a Lenovo PC last June that came with Vista preinstalled, and had to pay an additional $59.25 to have the system "downgraded" to XP.

"Microsoft has used its market power to take advantage of consumer demand for the Windows XP operating system by requiring consumers to purchase computers preinstalled with the Vista operating system and to pay additional sums to 'downgrade' to the Windows XP operating system," the suit alleges.