We catch up with the very busy Hilary Duff

It is an uncommonly ugly Monday in L.A. The rain can drench a human in seconds, so Hilary Duff is shielded with coats and umbrellas as she ventures from the makeup trailer to the soundstage where she’s filming an advertisement for VideoNow, a portable video player from Hasbro. As an incentive, the player offers an exclusive ”A Day in the Life of Hilary Duff” videodisc — a major enticement to the preteen audience at whom the players are targeted, and for whom Duff is a major preoccupation.

If you are above, say, 17, you may never have heard of her, but Duff’s TV series, ”Lizzie McGuire,” is among the top-rated cable shows with viewers ages 6 to 14. The show is winding down its 65-episode run, and a movie spin-off — cleverly titled ”The Lizzie McGuire Movie” — opened on May 2. It is the second of Duff’s four movies this year: She’s already been Frankie Muniz’s love interest in this spring’s ”Agent Cody Banks”; she’s currently filming a role as one of Steve Martin’s daughters in ”Cheaper by the Dozen”; and after that, she’ll play the lead in the self- explanatorily titled ”Cinderella Story.” On top of all that, her album, ”Metamorphosis,” is due in stores this fall, and her makeup and clothing line is scheduled to debut next spring. It is an impressive to-do list for a 15-year-old girl.

But on this particular day, her task is selling this $49.99 video player. As the afternoon drags by and the crew members begin grumbling, she recites one bit of ad copy after another, taking care each time to give the director three readings of each line: ”ONLY on VideoNow! Only on VIDEONow! Only on VideoNOW!” Finally, with her work on the advertisement complete, she tapes the intro for her ”Day in the Life” special. She’s given the line and repeats it quickly to herself a few times before looking into the camera. ”You know,” she says earnestly, ”some people might think that being my age and being an actress and a singer is a lot of hard work. And sometimes, it is. But most of the time, it’s a lot of fun!” And then she says it two more times.

Hilary Duff arrived in Los Angeles six years ago, at age 9, with her mother, Susan, and her older sister, Haylie. Hilary followed her big sister into acting: When both were grade school students in Texas, Haylie began taking acting classes and Hilary tagged along; after Haylie filmed a supporting role in a made-for-TV movie, the mother and her two daughters decided to head west and try their luck. Their father, Bob, stayed behind in Houston, where he is a partner in a convenience store chain. (He visits his family about once every three weeks.) Both girls met with initial success, landing roles in direct-to-video movies, and then found themselves idle for two years, which, Hilary says, enervated them no end. ”It’s almost like a craving or an addiction,” she says, reclining in her trailer for ”Cheaper by the Dozen.” ”You want to keep working.” In 2000, Hilary was cast in the pilot for a sitcom, ”Daddio,” only to be replaced when the show was picked up by NBC. She took the rejection hard: ”I was, like, wanting to quit,” she recalls, ”and I had one audition left, and it was ‘Lizzie McGuire.”’