As promised by Sony Ericsson last month, the boot loader unlock now available for certain releases of Sony Ericsson Android™ phone models from 2011 and onwards which will allow to install Custom ROM and other third party goodies. Hold your breathe, sadly Xperia X10 user will not be able to unlock the bootloader as clearly stated the unlock method only works with 2011 Xperia models like Xperia™ arc, Xperia™ neo, Xperia™ pro and Xperia™ PLAY. One thing more, even if you got one of these phone it should be SIM unlocked Smartphone as the carrier branded device are not allowed to modify. But hopefully the genius developers will give us a way around.
If you passed the conditions above you may head to Sony Ericsson unlockbootloader website where they put together a details guide how to do it. Also remember, you should only unlock the boot loader of your phone if you are an advanced user with good knowledge of the technology and risks involved. If you perform this step, you will unlock the boot loader and which may void your warranty. Stay tuned with us at Facebook and Twitter to keep yourself updated on latest Sony Ericsson Xperia development. source.