Hey I have finished the game and I have collected 42 Bronze Wizard Cards..

Hiya,
Behind the door is a selection of rooms with the gold cards dotted around, so basicaly you need to get all of the silver cards to get the golds. However in this game if you miss any of the silver cards you can buy them of students at the end of the game!
Hope that helps!

First you have to collect all the Silver ones and then go to the door at the first floor room.It will open because each ten cards (Silver)are used as one key.You need 40 cards.When you enter this room move forward and enter a door after the curtains.the cards are in there.There is time to finish it but you can try again if you don't make it.The last card is Harry Potter.Each card you collect will appear in the room with the curtains.

I can remember finding 1 or 2 that aren't in that room but I do not remember where I found them.

After you have collected all of the silver cards go to the first level, nearly headless nick showed you this room at the start of the game, and go to the door with the silver card shapes on it, it will unlock a room where all of the gold cards are located,you should recieve a key for every 10 silver cards you recieve, each key unlocks a board to the room. I hope this helps.