In order to hard reset a BenQ-Siemens S81, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
BenQ-Siemens S81 device will be brought back to the default configuration of a brand new device.
1. Turn on the phone.
2. Type in this uber extra super secret code: *#9999#
3. Do nothing until your phone restarts. Congrats, you have performed a hard reset. Yay.