Hard Reset SONY Xperia M2 dual D2303

First method:

1. First of all make sure that your cell phone is switched on. 
2. In the next step go to Settings and then to Backup & Reset.
3. Tap Factory data reset and Reset Phone. 
4. Afterwards choose Erase Everything if you are sure you want to clear all your data. 
5. Select OK to confirm the whole operation.
6. Well done! The hard reset has just been performed.

Second method:

1. Download program named flashtool from Sony website:http://developer.sonymobile.com/services/flash-tool/
2. Then check, that you have installed drivers for your USB data cable.
3. Now switch off your handset.
4. Afterwards press and hold Volume Down, and connect to USB cable.
5. Accept all informations.
6. Success

Third method:

1. You should first download and install program PC Companion.
   * In example from here: http://www.sonymobile.com/gb/tools/pc-companion/
2. If all went well, you will see window with 4 options.
   
3. Click "Start" under the name "Support Zone New!".
4. Wait until the installation process is completed.
5. Now you should see window with "Phone / Tablet Software Update".
   
6. Accept this option -> click "start".
7. Then select "repair my phone / tablet".
8. Please follow all instructions, and confirm that.
   
9. Read "Inportant information", and confirm.
   
10. Afterwards PC Companion is "preparing computer for software update".
    
11. Select your phone / tablet model.
    
12. Follow steps, which you see in new window.
    
13. That's all!

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.