Like a virgin’s padded bra, Harry Potter and the Deathly Hallows, Part I is all tease, zero payoff. No investment banker left standing could fail to applaud the studio’s initiative in halving the seventh and last book in J.K. Rowling’s Harry Potter series to squeeze the goose for more gold. But a movie that plays like a 146-minute trailer for the actual final chapter — Part II opens next July in 3D! — is a definite cheat. For starters, there’s no Hogwarts. Harry (Daniel Radcliffe), Ron (Rupert Grint) and Hermione (Emma Watson) spend this movie on the run. They’re searching for the four Horcruxes that contain pieces of the evil soul of Lord Voldemort (Ralph Fiennes). That’s all the plot you’ll get from me. Luckily, there’s a nifty animated piece inserted to explain the Deathly Hallows. In the film’s sagging midsection, director David Yates and screenwriter Steve Kloves strand our teen love triangle in the woods, mooning over who is hot for whom. Yawn. There are compensations. Radcliffe and Watson share a sweet dance. And Grint, funny and touching, steals the show as jealous Ron. As for Dobby, rock on, Elf boy. Still, there’s nowhere near enough of the scheming Severus Snape (Alan Rickman) and the Hitler Youth villainy of Draco Malfoy (Tom Felton). Part I is more disappointment than disaster. It merely rolls along like something off an assembly line. Untouched by human hands.