In order to hard reset a Siemens SX1, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Siemens SX1 device will be brought back to the default configuration of a brand new device.
1. Power up the device.
2. Type in this code, *#7370#, confirm, and then this code, 12345, confirm again.
3. Select Yes. Wait for your phone to reset & restart. Done.