Now Root Sony Xperia Arc S 2.3.4 with full detailed intructions .But rooting it is an attempt which break the security protection and warranty of your device.It will bring lot of benefit to user.After rooting device you can do whatever you want in your device.The following guide is only applicable for Sony Xperia Arc S phone that installed with firmware version 2.3.4.Steps to keep in mind Before rooting :
1.Unlock the bootloader file of your Xperia Arc S
2.Charge your tablet to 60% or above.
3.Create a full backup of your data including contacts,sms,settings and apps.
4.Also remove or disable antivirus apps in your computer because it may interrupt the rooting process.
5.Enable USB Debigging mode by navigate to Settings>Applications>Development.
ROOTING STEPS :
1.Go to Settings>About Phone and select the model number and build number.If (4.0.1.A.0.283) displayed,this is to make sure that phone is compatible with this tutorial.
2.Download pre-rootedAndroid 2.3.4 and fastboot with Android USB file.rar in your computer and save it.
3.Turn Off your handset.
4.Extract the fastboot.rar file.You should get two different folder named as fastboot and USB driver.Remember the ftf file that you have already download oin the first step.Move it to fastboot folder.
5.Now press and hold menu button while plug your phone into your computer.
6.The LED light should turn into blue.
7.Open fastboot folder and press shift key and click on the empty space inside the fastboot folder.This should make the command prompt launch.
8.Type the command:
fastboot flash system LT15i_4.0.1.A.0.283_Generic_Global_system.img
9.Press enter and see the 'finished' message in command prompt.
10.Unplug handset and turn it on.
11.Download Superuser app from Google play and the process complete.