The Wild Stallion
(Moore, OK, USA)
It's about a legendary horse named Dark Cloud. He was a derby stallion but escaped when a train got derailed. After being lost, he started living in the wild and is called the Black Stallion. Soon, two girls, Hannah (played by Miranda Cosgrove)and CJ learn of a plot that might jeopardize the Black Stallion and other wild horses.
P.s. You can watch it online at http://www.watch-movies-online.tv/movies/the_wild_stallion/ if you can't buy it anywhere. I found it while I was looking around for a good movie.