Game crashes: questions and answers.

I tried to activate it by modifying some files (I don't remember the format) using Notepad.

You need to restore them to their original state (maybe something extra was written, or something was deleted):
1) Manually restore them to their original state.
2) Get these files from someone else and replace them.
3) Delete the profile and reinstall the game (sometimes, the game doesn't delete manually modified files).
4) Simply delete the profile from "My Documents" and create a new one in the game.

Try one of these options.