Rooting the Acro S the easy way

This tutorial is Originally posted by heeroyun on xda

You need:
Rooting kit: HERE
Flashtool 0.9.0.0
The Acro HD (SO-03D) 2.3.7 files: HERE
The Acro S 4.0.4 file:HERE 

Link for whole pack: HERE

Prepare:

(1) Application Settings: [Unknown sources] checked {Allowed}
(2) Application Settings: Development [USB debugging] checked {Allowed}
(3) Application Settings: Development [Stay awake] checked {Allowed}
(4) Settings -> Display settings [Screen timeout] Set to 30 minutes
*If your screen goes off just once then you won’t be able to return to the installation properly. Very important!!
Please think about your battery and try to keep the display brightness to a minimum.
(5) Please use a regular picture for the background. Do not use the default live wallpaper.
(6) Charge the Xperia S’s battery to 80%.

How to:
- Turn off the Acro S. Prepare to flash the 2.3.7 file: check all of the Wipe column, uncheck the rest.
- Plug in the Acro S while holding the volume down. Wait for the flashing to be completed and close Flashtool
- Turn on the Acro S. Connect it to computer via USB with USB debugging mode on.
- Run step1.bat
- Flash 4.0.4 files using Flashtool, don't wipe anything, also check no final verification. Close flashtool after finished.
- Turn on the Acro S. Connect it via USB.
- Run Step2.bat
- You should get a lot of messages like "pushing SuperSU" and the phone will reboot during this process.
- Enjoy full root