Activating this trainer:
If not state otherwise below, press F1 at main menu.
Listen for 'Trainer Activated'.
Press desired hotkey. All hotkeys can be changed on the trainer.
NumPad1: Reset Demo Clock
NumPad2: Zombies Don't Attack
NumPad3: Unlimited Ammo
NumPad4: No Reload
NumPad5: Super Speed
Reset Demo Clock: Once you are in the game and playing, toggle this on and the clock resets. Note that if you already have the achievement for 30 minutes of gameplay, or you have other achievements for certain times, the game may need you to completely delete your achievements and your savegame to fully reset. Do a search online. Basically, if you can start the game, then toggle this on and you have unlimited time to explore the demo.
Zombies Don't Attack: Toggle this on BEFORE encountering any Zombies, and generally they will not attack you.
Unlimited Ammo: Toggle on and you have unlimited weapon ammo.
No Reload: Toggle on and your gun has unlimited ability to fire rounds without reloading.
Super Speed: Toggle on to speed up the game time to fully explore and move about the map faster.