Adapting a literary masterpiece for film is a formidable challenge for directors and producers. But what if the classic work is a 17th century Spanish novel, Miguel de Cervantes' Don Quixote de la Mancha, being adapted for a modern English-speaking audience? And what if the filmmakers are adapting their script from a Broadway musical, Dale Wasserman's +Man of La Mancha, loosely based on the original Cervantes work? The result, in the case of director Arthur Hiller's film about demented idealist Quixote, is an adventure into the bizarre. Here is a motion picture in which the great dramatic actor Peter O'Toole (Quixote) is reduced to lip-synching the Mitch Leigh-Joe Darian song "The Impossible Dream." Even worse, here is a film in which Sophia Loren (Dulcinea) sings in her own voice. Though the story is set in Spain, the motion picture unfolds in Italy with English and American actors in the main roles of Quixote and his feather-brained sidekick Sancho Panza (James Coco). What's more, though the film is in widescreen format with color by Deluxe, a combination that invites spectacular imagery, the costumes resemble garage-sale leftovers, and the setting for half the film looks like a dark and dingy dungeon. (In fact, it is a dungeon.) As for the main purpose of the Cervantes book -- to lampoon other writers who dwell nostalgically on the age of knight-errantry -- one may find traces of it when O'Toole falls off a horse or jousts with a windmill. Surprisingly, it is possible to sit through this film. O'Toole is good when he's doing what he was cut out to do: recite lines, not sing them. And Coco is sometimes endearingly cuckoo. Then there is the music score, which was nominated for an Academy Award. So what we have in Hiller's Man of La Mancha is a bad film with good moments -- or, in the opinion of a few brave critics, a good film with bad moments.