Hard Reset SONY Xperia U ST25

First method:

1. Switch off the handset.
   
2. Now navigate to Settings -> Backup & reset -> Factory Data Reset -> Reset Phone.
3. Then choose option option "Erase everything", and confirm that.
4. Success!

Second method:

1. Power off the device.
   
2. Next hold and press Volume Up + Volume Down + Power button until you see menu.
   
3. 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.
4. Now you will see yellow triangle and Android logo.
5. Then press Volume Down + Volume Up to see menu.
   
6. Please use Volume buttons to browse option "wipe data / factory reset", and confirm that using Power button.
7. Select option "Yes -- delete all user data".
8. After that accept "reboot system now".

Third method:

1. Turn off your cell phone.
   
2. Now press and hold Volume Down.
   
3. Then press and release Power button.
4. Next you will see menu.
5. Choose option Clear Storage using Volume Down to scroll, and Power button to confirm.
6. Press Volume Up to confirm operation.
   

Fourth method:

1. Back up your important files, and download PC Companion from here:http://www.sonymobile.com/gb/tools/pc-companion/
2. After installation you will see window with 4 options.
   
3. Now hover your mouse over the option "Support Zone Now!" and click "Start".
   
4. Next plese wait, until your program Install a suitable additive.
5. Afterwards from the window with 3 options choose "Phone / Tablet Software Update", and click "Start".
   
6. Then click to "repair my phone / tablet".
   
7. Accept all informations.
   
   
8. Now your program will run "preparing computer for software update".
   
9. Select your model.
   
10. After that you will see window with informations.
    
11. Follow the instructions, and connect your device into your Personal Computer.
12. Success!

Fifth method:

1. Make sure, that your phone is off.
2. Press and hold Volume Up + Home key + Power button together.
   
3. When you see logo of your phone, then release holded buttons.
4. Now use Volume Down to go down, and Home key, or Power button to select.
5. Select option "wipe data / factory reset".
6. Next choose "Yes -- delete all user data".
7. After that select "reboot system now".
8. Success!

Sixth method:

1. Check your device, that is it on.
2. Now press the phone's dialer and tap this: *2767*3855#
3. Then confirm all information on your screen.
4. Done!

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