Disney animators and filmmakers have again expanded the boundaries of imagination with "Fantasia 2000!" Fulfilling Walt Disney's original vision of fusing sight and sound in a full-length motion picture, "Fantasia 2000" begins where its predecessor, "Fantasia," left off -- with seven completely new segments adn the return of the popular "The Sorcerer's Apprentice."      In this fun-filled, imaginative movie, breathtaking images are coupled with classical music favorites. From Beethoven to Gershwin -- from flamingos playing with yo-yos to a city in bluesy motion -- vivid animation brings the music of the masters to colorful life.