Microsoft had not filed a response to the complaint and a spokesperson could not immediately be reached. [Update, 9:04 a.m.: Spokesman David Bowermaster said via e-mail: "We have not yet been served with this lawsuit, so it would be premature to comment."]

In the complaint, Alvarado's attorneys allege:

"As the sole licensor of Windows Vista, Microsoft enjoys vast power over OEMs which it has used and continues to use to stifle competition. ... Microsoft has used its power to coerce OEMs, internet access providers ("IAPs") and others into agreeing to restrictive and anti-competitive licensing terms for its Windows XP operating system in order to stifle competition in the market. ...

"Consumers have encountered numerous problems using the Vista operating system, and these problems have been widely publicized in various media outlets. As a result, many consumers would prefer to purchase a new computer pre-installed with the Windows XP operating system or at least not pre-installed with the Vista operating system. However, Microsoft has used its market power to take advantage of consumer demand for the Windows XP operating system by requiring consumers to purchase computers pre-installed with the Vista operating system and to pay additional sums to 'downgrade' to the Windows XP operating system. ...

"To date, nearly one in three consumers purchasing a new computer has paid to downgrade the operating system from Vista to Windows XP."

They allege the company violated:

• the Washington Unfair Business Practices Act, by operating an unlawful trust that limited competition and inflated prices for Vista and XP, and kept PC makers from pre-installing XP;
• the Washington Consumer Protection Act;
• the Washington Business Practices Act.

The plaintiff is seeking treble damages and legal fees, and asking the court to stop Microsoft from engaging in the anti-competitive behavior alleged in the complaint.

The proposed class includes U.S. residents who "purchased a computer with the Windows Vista
operating system for their own use and not for resale at any time during the four years preceding the date of filing of this complaint and paid to downgrade to the Windows XP operating system."

By the way, is U.S. District Court Judge Marsha Pechman becoming one of the most experienced judges in the country when it comes to the nuances of recent Windows operating systems?

This case is in her court, as is the ongoing Vista Capable class action lawsuit, which is nearing a make-or-break moment. Pechman told the Vista Capable parties on Jan. 22 that she would rule on Microsoft's motions to dismiss the suit in about 2 1/2 weeks -- roughly now.

Credit to the Seattle P-I's Joe Tartakoff, who first reported the XP downgrade suit.