PS2 Harry Potter and the Half-Blood Prince Cheats
 

Unlock Castle Gates Multiplayer Dueling Area
Enter this code at the Rewards Menu: RIGHT, RIGHT, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT, LEFT, RIGHT, START

Hogwarts Crest Rewards
Collecting the crests hidden around Hogwarts unlocks the following rewards:

3 Crests - Two Player Dueling Pack 1: Draco & Luna
8 Crests - More health in duels
14 Crests - Two Player Dueling Pack 2: Training Ground Dueling Arena
21 Crests - Dungbombs in prank boxes around Hogwarts
29 Crests - Two Player Dueling Pack 2: Crabbe & Goyle
38 Crests - Score boost in flying events
48 Crests - Exploding Cauldrons in prank boxes around Hogwarts
59 Crests - Two Player Dueling Pack 4: The Transfiguration Dueling Arena
71 Crests - Max health in duels
84 Crests - Two Player Dueling Pack 5: Ginny & Hermione
98 Crests - Love Potion in Potions Club
113 Crests - Two Player Dueling Pack 4: Paved Courtyard Dueling Arena
129 Crests - More mini-crests with each cast

sumber