How to Find the Professor in LEGO Harry Potter for the PS3

Press "Square" beside any golden cauldron, and then select any dark magic user to switch to that character. For example, you can be Voldemort or Malfoy.

Navigate to the Defense Against the Dark Arts classroom. Hold "Triangle" to open the spell wheel, and then pick "Dark Leviosa" as the active spell.

Press "Square" to cast Dark Leviosa against the dark gate in the back of the room. This destroys the gate, granting you access to a door. Exit through the door.

Switch to your Immobilus spell. Press "Square" to cast the spell at the Pixies, moving the clock pendulum blocking your way. This stops the pendulum, allowing you to walk around and jump across the platform to the next pendulum. Repeat this until you get all the way across the room.

Walk down to the lower floor where more Pixies are moving platforms across the way. Cast Immobilus on each Pixie before jumping onto the next platform. Continue this until you reach the other side, where an orange chest rests.

Switch to your Reducto spell, and then cast it at the orange chest, revealing the Professor Quirrell token. Press "Start" and select "Leaky Cauldron." Confirm your decision and wait for the level to load.

Enter Diagon Alley through the north door, and then enter Madam Malkin's Robes. Purchase Professor Quirrell for 150,000 studs.