Sony Ericsson has just made a major step in the right direction, when it comes to Android ROM customization. They’ve just opened a website for bootloader unlocking, specifically meant for Xperia devices. This means that it’s official and OK to unlock the bootloader on your Xperia Arc and Xperia Play and use custom ROMs.
There’s a guide on how to do this right here and keep in mind that not all of the phones support this solutions, including some sim-locked devices. A guide over here shows you if the handset you’re using is compatible. All you need to do is enter a name, email address and the first 14 digits of the handset’s IMEI number to get started.
However, there’s always that warning from Sony Ericsson, recommending you NOT to unlock the boot loader, but that’s just official talk, to excuse any software failures. There’s also a Legal Terms box in there, letting you know about warranting voiding and whatnot… After all this is completed, you will get the needed code.