I just bought the same one at WalMart. I bought the display model and they forgot to give me the "Safety Key".
It's a round red "button" type thing that has magnet on the bottom and it fits directly under the control panel where it says stop. It has a cord on it so that if you start to fall you can pull it and it stops the treadmill. Mine would not come on without it.
K.Flinn
August 2008