Half-Blood Prince broke the record for midnight box office sales. WB has announced how well Half-Blood Prince did in its first 24 hours: Warner Bros.' "Harry Potter and the Half-Blood Prince" grossed a magical $58.4 million from 4,275 theaters as it opened Wednesday at the domestic B.O., including a potent $22.2 million in midnight shows. Film was pacing well ahead of the $44 million earned by "Harry Potter and the Order of the Phoenix" on its opening Wednesday exactly two years ago. "Order of the Phoenix" posted a five-day opening gross of $139.7 million. "Half-Blood Prince's" midnight runs were the best ever for any film, besting the $18 million earned by Warners' "The Dark Knight" last summer, as well as the $16 million grossed by Paramount's sequel "Transformers: Revenge of the Fallen" earlier this summer.