For the second year in a row, they're packing 'em in at the New York Music & Internet Expo, a show dedicated to digital music and the people who love it. Promoter Steve Zuckerman said he's expecting 5,000 people to pass through the New Yorker Hotel ballroom by Sunday night (March 5), when funkmaster Nile Rodgers delivers his closing speech. MP3 and custom-CD companies are crowding the exhibit floor, and Zuckerman said he had to turn down 150 more who wanted to rent space. Next year, the show's moving across the street to Madison Square Garden, he added. Danny Goldberg, ex-head of Atlantic and Polygram, kicked off the show Friday morning by telling webmasters to promote music instead of opinions about music, and stars instead of technology. "This is show business," he said.