In order to hard reset a Samsung N400, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Samsung N400 device will be brought back to the default configuration of a brand new device.
1. Power up the device.
2. Tap this code into the phone: *2767*3855#
3. Wait until the device resets and restarts.