How to Root Xperia Arc without unlock the boot loader
Now, Sony Ericsson Xperia Arc successfully to root without unlocking the bootloader. It is important because when you unlock your bootloader, you may void your warranty than you could charge by Sony Ericsson when you ask them to repair the phone.
Rooting the phone is very important since many of Android apps need to gain the root access to the phone. So, with this method, you could access more to the phone without sacrifice the warranty.
The rooting method for Xperia Arc without unlocking the boot loader is very easy. What you need is just download the gingerbreak .apk file to your phone, install than run the app. You will ask by gingerbreak to root the phone or vice versa.
If you get error message like “could not extract assets” just execute following command;
# adb shell rmdir /data/local/tmp
# adb shell mkdir /data/local/tmp
Done, you have root access with original boot loader on your Xperia Arc.

[...] can use the gingerbreak method, Superoneclick and Z4Root. Special for Xperia Android phone, you can rooted the phone without unlock the bootloader to ensure your warranty still [...]