[Sony Xperia P, U, Sola, Go] Shahad1230:
unlock your bootloader by these ways-

1)install usb drivers of xperia u..

2)Download Fast Boot Package (With USB Drivers)

3)Switch Off Your Device & Connect It To The Computer Using USB Cable While Enabling Fast Boot Mode (Press & Hold Volume Up Button To Trigger Fastboot Mode). Windows Will Start Driver Installation As soon As You’ll Connect Your Device To The Computer While Keeping It In Fastboot Mode.

3)Now Extract The Fastboot Package You’ve Just Downloaded.You Will Find 2 Folders Named As ‘fastboot’ & ‘usb_driver’.

4)Point Driver Installation Location To ‘usb_driver’ Folder.

5)Once Drivers Get Installed, Disconnect Xperia U From PC & Power On It.

6)Before Unlocking Bootloader, You Need To Check That if Your Device’s Bootloader Can Be Unlocked Or Not. For Checking Bootloader Status Dial *#*#7378423#*#* From Phone Dialer To Access Service Menu.Find Bootloader Unlock Status Over There. If It is Set To Yes Then Only You Can Unlock Your Device’s Bootloader Otherwise It’s Impossible To Unlock It.

7)After Verifying Bootloader Unlock Status Set To Yes, Go To Sony’s Official Bootloader Unlocking Site.

8)Scroll To The Bottom of The Page & Press Continue.

You Will be Prompted With The Message “Are You Sure ?”. Accept It By Clicking On “Yes I Am Sure”.(Assuming That You’ve Read It Properly). Then Accept The Legal Terms.

Now You’ll Get “Create Unlock Request” Page.Enter Your Name, Email Address & IMEI (Which You’ve Noted in Essential Steps Mentioned Above).

You’ll Now Get Unique Key Which Will Be Displayed On The Screen. Save It Safely As We Will Require It In Next Part Of The Article.

9)Open Command Prompt In Your Computer & Point/Set It’s Location To ‘fastboot’ Folder.

Again Connect Your Device To PC By Enabling Flash Mode On It..

10)Now In Command Prompt (CMD) Type The Following Command :

fastboot.exe -i 0x0fce getvar version

11)If Value is Returned (It Should return 0.5), It Means Device is Connected Properly.

Type This Second Command Mentioned Below :

fastboot.exe -i 0x0fce oem unlock 0xKEY (on the place of KEY give the unique key you have got in step 8) and hit enter..

YOUR BOOTLOADER IS UNLOCKED.. :victory:

---------- Post added at 02:43 PM ---------- Previous post was at 02:32 PM ----------

Procedure to Install Cyanogenmod 9.3 on Sony Xperia U ST25i:

1)Custom Recovery like Clockworkmod must be installed in order flash this ROM.

2)Download latest Cyanogenmod 9.3 package from any site (Cyanogen10 has not yet been released for xperia u)

3)Download Google Add-on Apps (Gmail, Maps, GTalk, Play Store etc.) which are not present in ROM by default.

4)After downloading CM9.3 package, connect your device to PC. Enable mass storage mode on it. Now transfer ROM package & Google Apps to your device’s internal SD card.

Now disconnect the phone from computer. Boot in recovery mode on your phone. To do so, switch off the phone, switch it on again, when phone is restarting (during boot logo & LED turns blue), press Volume up button. Your phone will land in recovery mode.

5)Take a nandroid backup of your current ROM so that it can be restored back (in case if anything goes wrong). To backup your current ROM, select Backup and Restore option from the recovery mode & on next screen, select backup. Now It will make a nandroid backup of your whole system (excluding SD card). Wait for the backup process to get finished.

6)Now Select “install zip from sdcard” & then “choose zip from sdcard“. Navigate the ROM file (which you’ve transferred earlier) Select it & press on ‘Yes‘ to continue. ROM installation process will start.

Wait for the ROM to get installed. After ROM gets successfully installed, your phone will land in the recovery mode again.

(Optional) The same procedure you have to do for installation of Google Apps. (Just don’t do the above step i.e, wiping data after installation of Gapps). After you finished installation of Gapps, press back button to go to main menu of CWM.

7)Select wipe data/factory reset & wipe cache partition to wipe all the data & caches from the phone memory respectively.

Select reboot system now from the recovery mode to Restart the phone. Switch off it again.Now download the ADB & fastboot files which we will need to flash the kernel image.

8)Extract above rar file to a convenient location/folder (Fastboot Folder).

Open Cyanogenmod 9.3 ROM package using WinRAR or 7-zip, extract boot.img file (which is nothing but a kernel) to any convenient location. (It is located in the root directory of the ROM).

Now move the kernel file (boot.img) where ADB & fastboot files are located.

9)On the phone (while switched off), enter into the fastboot mode. To do so, Connect your phone to the computer. While connecting press Volume up button to trigger fastboot mode.

10)Open the folder which contains ADB & Fastboot files.

Run commandprompt.bat file to open command prompt pointing to the ADB & Fastboot folder.

Type the following command in command prompt to flash the kernel file:

fastboot flash boot boot.img

11)Restart the phone by typing “fastboot reboot” (without quotes) in command prompt.

FINALLY YU WILL HAVE CYANOGEN9.3 CUSTOM ROM IN YOUR PHONE...:victory: