WASHINGTON -- Six state attorneys general not involved in the Microsoft antitrust case sent a letter to Microsoft executive Steve Ballmer this week expressing concern about the upcoming Windows XP operating system. The letter was originally drafted by a lobbyist for Microsoft's competitors.

Vermont Attorney General William H. Sorrell wrote that the operating system, which will reach consumers soon, "may involve additional unlawful attempts by Microsoft to maintain its operating system monopoly."

The Justice Department and the 18 states suing Microsoft have said they want any penalty stemming from the four-year case to cover Windows XP.

"Microsoft may have constructed this new product without due regard for relevant legal rulings, and without due regard for other issues involving consumer choice and consumer privacy," Sorrell wrote on behalf of his state as well as Arkansas, Maine, Montana, New Hampshire and Rhode Island.

The letter could increase pressure on Microsoft to change Windows XP, which includes many features that replace competitors' stand-alone products. On Thursday, Microsoft and prosecutors said they were talking about a settlement. A federal judge will set a schedule for penalty hearings next week.

An electronic copy of the letter reveals that the original author is Jeffrey Modisett, a former Indiana attorney general who is currently a lawyer for Manatt Phelps & Phillips. The firm represents Microsoft rivals Oracle and AOL Time Warner, and the head of an anti-Microsoft group confirmed that Modisett has worked as an advocate against Microsoft as well.

Microsoft spokesman Vivek Varma blamed AOL Time Warner for the letter.

"It's a shame that AOL has this much influence in the process," Varma said. "That doesn't seem to be in the best interest of consumers."