In order to hard reset a HTC Touch Diamond2, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
HTC Touch Diamond2 device will be brought back to the default configuration of a brand new device.
3. Keep holding the Volume Down button and press the Volume Up button just once.
4. Your phone will now return to its default settings after reseting and restarting. Well done.