1. First download and extract DooMLoRD ADB drivers
2. From DIR /Files execute file ADB.exe and wait to install
Without this drivers your SE xperia ARC S was not been recognized...
3. Connect your Xperia ARC S with USB cable
In your Xperia ARC S must be checked installation from UNKNOWN SOURCES and USB DEBUGGING, also phone must be in state MSC MODE
SETTINGS>XPERIA>CONNECTIVITY>USB CONNECTION MODE>MSC MODE
SETTINGS>DEVELOPER OPTIONS>USB DEBUGGING
Dont allow PC Companion to be installed on your PC.
4. Download and start eRoot v1.3.4
5. Press -root and wait to process be compete.
For confirmation of succeeded ROOT-ing Super User app has been installed