STEPS: Download any Custom ROM for Xperia P. You can get a Index of ROMs, Kernels etc from here . Do read instructions in the thread because every ROM may have a different requirement of Kernel and way of installing but basic idea is same. Place your ROM i.e. xxx.zip file in your Root of SDCard (in internal storage) Power off the device Power on and repeatedly press volume down (-) button after SONY logo appears until you see the recovery Now to clear cache scroll down to wipe cache partition and select it and scroll down to yes To clear data or do a factory reset scroll down to wipe data/factory reset and select it and scroll down to yes To clear dalvik cache scroll down to advanced select it again scroll down and select wipe dalvik cache After you perform all the steps press back to enter main menu Scroll down to install zip from sdcard and select it Scroll down to choose zip from sdcard and select it Now scroll to the ROM i.e. xxx.zip and select it and scroll down
Unlocking your bootloader allows you to flash a custom kernel i.e. kernel made by some developer rather than the stock SONY kernel. Flashing custom kernels allows you to flash CUSTOM ROMS like Cyanogenmod ROMS which have very vast features and user experience with imporoved performance, features and battery life. Note: Unlocking Bootloader of Xperia P Will Void It’s Warranty Provided By The Manufacturer (Warranty Can Be Retained By Relocking The Same). But DRM keys are lost forever if you unlock your bootloader i.e. some apps like TrackID, download mucis info in walkman app etc. doesn't work and also you would not get any OTA firmware update after you unlock your bootloader and also if you relock afterward STEPS: Firstly Get & Note Down IMEI Code of Your Device. It can be Obtained by Dialing *#06#in Phone Dialer. Charge Your Phone upto 60% Battery Level So As To Ensure That It Doesn’t Turn Off During The Process of Bootloader Unlocking. Temporarily Disable Your PC’s Antivirus S