Debug Mode Cheat
Open game.ini in the game's system folder with Notepad and find the following lines:
[HGame.baseConsole]
bDebugMode=False
bUseSystemFonts=True

To activate the debug mode change bDebugMode=False to bDebugMode=True.

Once the debug code is activated, press one of the following keys during gameplay to activate the corresponding cheat function:

[F4] - Select Level
[Delete] - Ghost Mode Toggle (use arrow keys to move forward/back; mouse to steer)
[Page Up] - Increase Game Speed
[Page Down] - Decrease Game Speed
[F9] - Get All Spells
[F6] - Restore Health

You can also set various things by pressing [~] during gameplay and typing the codes below to activate the cheat (press enter after each):

Set Wiggenweld Potion Amount: set statusitemwiggenwell ncount 1-9999999
Set Jellybeans Amount: set statusitemjellybeans ncount 1-9999999
Set Gryffindor House Points: set statusitemgryffindorpts ncount 1-9999999