Crest Roundup You can find extra Crests when you've completed Harry Potter's adventure. At some places in Hogwarts you can find firework boxes. If you burn these with Incendio, they will explode and a broken Crest will pop out. Repair it with Reparo and pick it up. (For instance, check out the box nearby the duel club of Hufflepuf)
More Harry Potter and the Half-Blood Prince cheats at: Cheat Masters