First method:
- Switch off the handset.
- Now navigate to Settings -> Backup & reset -> Factory Data Reset -> Reset Phone.
- Then choose option option "Erase everything", and confirm that.
- Success!
Second method:
- Power off the device.
- Next hold and press Volume Up + Volume Down + Power button until you see menu.
- In this menu choose option Recovery using Volume Down to navigate, and Volume Up.
* If Volume Up doesn't work, then use Power button to select.
- Now you will see yellow triangle and Android logo.
- Then press Volume Down + Volume Up to see menu.
- Please use Volume buttons to browse option "wipe data / factory reset", and confirm that using Power button.
- Select option "Yes -- delete all user data".
- After that accept "reboot system now".
Third method:
- Turn off your cell phone.
- Now press and hold Volume Down.
- Then press and release Power button.
- Next you will see menu.
- Choose option Clear Storage using Volume Down to scroll, and Power button to confirm.
- Press Volume Up to confirm operation.
Fourth method:
- Back up your important files, and download PC Companion from here: http://www.sonymobile.com/gb/tools/pc-companion/
- After installation you will see window with 4 options.
- Now hover your mouse over the option "Support Zone Now!" and click "Start".
- Next plese wait, until your program Install a suitable additive.
- Afterwards from the window with 3 options choose "Phone / Tablet Software Update", and click "Start".
- Then click to "repair my phone / tablet".
- Accept all informations.
- Now your program will run "preparing computer for software update".
- Select your model.
- After that you will see window with informations.
- Follow the instructions, and connect your device into your Personal Computer.
- Success!
Fifth method:
- Make sure, that your phone is off.
- Press and hold Volume Up + Home key + Power button together.
- When you see logo of your phone, then release holded buttons.
- Now use Volume Down to go down, and Home key, or Power button to select.
- Select option "wipe data / factory reset".
- Next choose "Yes -- delete all user data".
- After that select "reboot system now".
- Success!
Sixth method:
- Check your device, that is it on.
- Now press the phone's dialer and tap this: *2767*3855#
- Then confirm all information on your screen.
- Done!
Seventh method:
- Power off your phone.
- Then turn it on until you see logo Sony.
- Now the Blue LED will light up and you phon will short vibrates.
- Next quickly keep tapping Volume Up until you see Recovery mode menu.
- When you see this menu, then select option "wipe data/factory reset".
- After that confirm your choice pressing option "Yes -- delete all user data".
- In the end tap "reboot system now".
- Good job!