Although an MP3 version of Tom Petty's single "Free Girl Now" was pulled from the "MP3.com" website after just two days last month, Petty's label, Warner Bros., has returned to the site to make a promotional offer. In what the site says is the first time a major label has supported a promotion there, fans can buy Petty's new album, Echo, through "MP3.com"; fans who are performers are also being invited to cover one of the album's songs in the MP3 format. Petty will choose his favorite cover, and that performer will open for him and the Heartbreakers at a concert this summer. Before it was yanked off the website, "Free Girl Now" was downloaded 157,000 times. Although it's never been clear who made the decision to pull it, Petty told talk-show host David Letterman Tuesday, "There was a casual elbow in the ribs that 'maybe you shouldn't do this, Tom.' "