HOUSTON - Filmmakers tend to embellish the rough nuggets they find when mining real life. They have a story to tell and a product to sell, so nothing can get in the way - even the facts.

"Hidalgo" - with Viggo Mortensen in the saddle as the top-billed star for the first time - purports to tell the true tale of a heroic American cowboy in a desert race. But guess what? It may never have happened.

According to the Long Riders' Guild, an international equestrian group, the film's Frank T. Hopkins (Mortensen) was a "counterfeit cowboy" who invented the tales he published decades after his alleged feats. The guild punctures Hopkins' claims in an exhaustive study for the book "Hidalgo and Other Stories."

Similarly, the Council on American-Islamic Relations slams the film for stereotyping Muslims and Arabs and for presenting as fact a race that didn't exist. Other sources say there's not even any evidence that Hopkins ever set foot in Arabia, where he claims to have won a 3,000-mile "Ocean of Fire" race on his mustang, Hidalgo, against bigger Arabian horses.

Of course, "Hidalgo" is just a film, and as sheer popcorn-munching fun, it's an often-rousing action-adventure that confirms Mortensen as a star. When the movie stumbles, it's not his fault.Not that "Hidalgo" gives him anything as meaty as his career-defining work in the "Lord of the Rings" trilogy. But instead of overcompensating, Mortensen wisely underplays, easing into the role of the laconic cowboy with low-key dignity. Between action scenes, which he handles quite well (you expected less after "Rings?"), it's a performance of charming understatement.The film is less embraceable as a sprawling adventure. Not only are its fictional roots showing, they're the same old color as too many movies.The only history "Hidalgo" can claim may be cinematic. Director Joe Johnston ("Jurassic Park III") gallops with a stampede of proven elements, from the jaunty, nonthreatening perils of Indiana Jones films to the computer-generated sandstorms of "The Mummy" to the stark desert exoticism of "Lawrence of Arabia."At least its heart is in the right place. Old-fashioned action-adventures for the family are hard to find, and straddling a broad age demographic is hard to pull off. Nor does "Hidalgo" always succeed. Its violent tragedies may be too grim for small kids, while its innocent simplicity may not satisfy thrill-conditioned teens or adults, especially considering its leisurely pace.Like too many Disney flicks, "Hidalgo" plods along, starting an amble toward 2½ hours with a sustained back story at the start.We see a washed-up 1800s American hero who's tormented by the massacres he's seen and is drunkenly killing time in a Wild West show. How Hopkins and his mustang, Hidalgo, get to Arabia is the stuff of tall tales, but the yarn-spinning has only begun. Their punishing race against bigger horses is more of an endurance test than a need for speed. It also veers aside for a kidnapping, a rescue and a romance, not to mention much gabbing over philosophical divides.Johnston exploits the detours to punch up the excitement, but often at the expense of credibility. An attack by cheetahs, obviously computer-animated, is the worst cheat.But Hopkins' horse is for real, and he steals the show. Played by T.J., a mustang Mortensen wound up buying, the horse has uncannily humanlike reactions in key moments, providing gentle comic relief.Though the cowboy is irresistible to the film's few women, his bond with his horse stokes the story. "Nobody hurts my horse!" he says, thus boiling down his cowboy code to four words.Their touching bond is more appealing than any far-fetched gimmicks Hollywood can concoct. "Hidalgo" may be a bumpy ride, but the love and loyalty of its chief characters is warm and worthy, whether their story is factual or false.