White night mod ?!

[Ashtoreth]

As Neelke said, the best solution is to reinstall the game. However, after running the uninstaller (or after deleting the local content on Steam, depending on which version of the game you own), you have to manually delete the Amnesia The Dark Descent folder in order to remove the leftover files from the full conversion. The uninstaller will not remove them because those files aren't part of the main game.