In order to hard reset a Motorola A3100, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Motorola A3100 device will be brought back to the default configuration of a brand new device.
1. Turn on the phone.
2. Now open Menu, enter Setup and Master Reset.
3. Done, the phone should now reset & restart.