A lot of people who play Resident Evil are not the biggest fans of the One Dangerous Zombie mode! I recommend that you isolate one save-slot for missions with Chris Refield, one save-slot for missions with Jill Valentine and then one save-slot for a file where you have activated this mode (One Dangerous Zombie)! Ultimately, you get a greater variety (seeing as you are not compelled to play a game with this mode activated whenever you load a saved game-file) of gameplay without having to start a new file altogether!