The letters don't explicitly threaten a lawsuit against the universities. But they do include a copy of the groups' lawsuit against Napster, which contains a generic placeholder for adding new universities into the legal crosshairs.

In the first version of its suit, filed last April, Metallica named Indiana University, the University of Southern California and Yale University as defendants because they had allowed their students to download music using high-speed university Internet connections. After the suit was filed, all three of the universities backed away from their hands-off policies, and Metallica dropped them from the suit.

"There is no express threat in the letters that they're going to get sued," said Los Angeles attorney Howard King, who represents Metallica and Dr. Dre. "We're pretty comfortable that even without the threat of litigation that the universities will reach the same conclusion that Yale and USC have."

King's letters were initially sent to Harvard University, Columbia University, Stanford University and the University of Virginia. By the end of the day today, he will have sent similar letters to about 25 institutions, he said. The letters are going out to both the university presidents and the student newspapers, the attorney said.