Much of the book's ending has been changed, with the climactic battle and Dumbledore's funeral being removed. Heyman commented that the end battle was removed to "(avoid) repetition" with the forthcoming adaptation of Deathly Hallows. The scene where Harry, Ron, and Hermione using the invisibility cloak to sneak away from Arthur and Molly Weasley into Knockturn Alley to follow Malfoy was cut. The Death Eaters proceed through Hogwarts without any resistance with a crazed Bellatrix ravaging the Great Hall and setting fire to Hagrid's hut. The funeral was removed as it was believed it did not fit with the rest of the film.[63]
In the book, it is only hinted at that Hermione knows about Harry's feelings for Ginny. Also, Harry only realizes his feelings for Ginny later on in the book, though it is hinted at that he is attracted to her. In the book, the Amortentia love potion reminds Harry of "something flowery" from the Burrow, which is revealed to be Ginny. The potion makes scents which attract the person smelling it. In the movie, Harry starts to realize his feelings much earlier on. Also, the movie seems to focus a lot more on the relationship between Harry and Ginny than the book and includes several scenes showing their relationship that were not in the novel.
The destruction of the fictional Brockdale bridge mentioned briefly in the book is transferred to the real Millennium Bridge in London, which is made to fluctuate more and more wildly until it breaks; this serves as the film's opening sequence. Given the book's timeline of 1996-1997, the Millenium Bridge would have yet to exist, construction having begun in 1998 and opened in 2000.
A few additional scenes were included. Instead of awaiting Dumbledore's arrival at the Dursleys' like in the novel, our re-introduction to Harry is inside a railway station cafe, where he is shown reading a Daily Prophet article about Lucius Malfoy's imprisonment and subsequently flirting with a waitress. Correspondingly, Dumbledore's arrival is a surprise to him. Also, scenes of Diagon Alley being demolished by Death Eaters and an attack on the Burrow, known as "The Burning of the Burrow" by Bellatrix Lestrange and werewolf Fenrir Greyback are added. During their attack on Diagon Alley, the Death Eaters are seen abducting the wandmaker Ollivander. All but two of the memory scenes, including that of the Gaunts, have been cut. Only the flashbacks of Tom Riddle at the orphanage and Riddle asking Slughorn about Horcruxes, shown twice, remain. Yates said they made the decision to compress the memories, but still "got some really cool ones".[64]
Characters who are cut include the Dursleys, Dobby and Kreacher, Bill and Fleur, Rufus Scrimgeour, the Gaunts, Cornelius Fudge and the Muggle Prime Minister.[65] All scenes involving these characters are either removed or replaced. Bill and Fleur's engagement is left out, as well as any mention of Rufus Scrimgeour taking over for Fudge as Minister of Magic (However there is a shot of the Daily Prophet shows that there is a new Minister of Magic). Dobby and Kreacher never tail Malfoy for Harry, the memories of Voldemort's mother's family (the Gaunts) are excluded (save for one mention of Merope Gaunt and her ring by Dumbledore), and the Death Eater attack scenes and the train station scene replace both a Fudge-Muggle Prime Minister conversation and a scene with the Dursleys, where Harry learns from Dumbledore that he inherited Number Twelve, Grimmauld Place in Sirius's will.
Why????
