Want to root your Xperia Arc S running on Stock ICS Firmware? No problem, here’s how you can do it.
1. You must be running on the stock ICS firmware.
2. Make sure your phone has at least 60% of battery life left to last through the entire process.
3. Close any Antivirus programs running on your PC as they can interrupt the rooting process.
1. Download the Root Toolkit from here.
2. Download the ADB Drivers from here.
1. Place the downloaded ADB Drivers file onto your Desktop.
2. Double-click the Flashtool-drivers.exe file to install the drivers.
3. Follow the on-screen instructions.
1. Place the downloaded Root Toolkit archive onto your Desktop.
2. Extract files from the Root Toolkit archive and place them on your Desktop.
3. Enable USB debugging on your phone by heading to Menu>>Settings>>Applications>>Developer Options>>Development>>USB debugging.
4. Enable Unknown sources on your phone by going to Menu>>Settings>>Security>>Unknown sources.
5. Connect your phone to your PC using the USB cable that came with it.
6. While the phone is connected to PC, just double-click the runme.bat file to begin the rooting process.
7. Follow all the instructions that are displayed on your screen.
8. After it has finished rooting your phone, you will get a message saying All Done.
9. You can now disconnect your phone from the PC.
Your phone should now be rooted and you can now install the apps which run on rooted phones only. You can install the popular ClockworkMod Recovery on your Xperia Arc S by downloading the CWM AutoInstaller app from Google Play Store.
If this procedure helped you, then please head to the official thread over at XDA forum to thank/donate to the original developer of this root method !