When the digitally shot, three-dimensional film Hannah Montana/Miley Cyrus: Best of Both Worlds Concert raked in $31 million on its opening weekend earlier this year, it served as both wake-up call and warning for the owners of the United States' 6,000 theaters, which are about to undergo the most expensive and risky makeover since movies went to sound or color.
  Studios and theater owners are going digital. If Hollywood and the Motion Picture Association of America get their wish, it could cost studios and theater owners upwards of $1billion. And there's no guarantee it will revive an industry that hasn't seen an attendance increase in the past three years.
  But that won't stop studios from trying...