7 - books
7 - years of Hogwarts
7 - horcruxes
7 - Weasley children
7 - Potters in Deathly Hallows
7 - players in a Quidditch team
700 - Quidditch fouls
7 - floors at Hogwarts
7 - tasks to get to the philosopher's stone
7 - secret passages out of the castle
7 - Harry's Quidditch number
7 - times Zabini's mother married
7 - prisoners in Malfoy manor
7 - locks on moody's trunk
7 - registered animagi in 20th century
7 - number of OWLs Harry and Ron got
7 - floor of Gryffindor common room
7 - snakes on the door to the chamber of secrets
7 - times voldemort tried to kill Harry and failed
7 - month mentioned in he prophecy