Harry Potter and The Changes of Chance: Book 1

William Strider is happy. He lives with his parents, and they use magic around the house. They want him for Hogwarts, and William wants to go there, and so he does. After a horrible accident, William goes to Hogwarts feeling depressed. There he meets Harry Potter, Ron Weasley, and Hermione Granger, who help him, and in return, he helps them. (Alternate Reality; Non-Canon)