Root Your Xperia Phone Without Voiding Warranty:

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Root Your Xperia Phone Without Voiding Warranty

Disclaimer: By following this methjavascript:void(0)od, you are NOT permanently modifying your phone and Sony Ericsson won’t have a “clue” that you are rooting your phone. You can perform a repair using SEUS to claim warranty at any time. I’m posting this for informational purposes only. Secondly, I won’t be responsible if you brick your phone, which is almost impossible.
If you have an Android device, or any smart phone for that matter, you can do almost anything that you can with a PC. As Android is an open source mobile operating system, it can be tinkered with in different ways. While Android, by default, doesn’t allow javascript:void(0)that, you can get root access to the OS and enjoy the full potential of your phone. In most of the Android phones, you need to unlock the bootloader in order to root it. But Sony Ericsson Xperia phones can also be rooted without unlocking the bootloader, thus preserving the manufacturer warranty.
This tutorial is based on this thread on XDA Forums. The tool we are going to use here is called DooMLoRD’s Easy Rooting Toolkit. The tool works very well until the firmware number 4.0.2.A.0.58. Sony Ericsson has patched the later ROM versions and hence this method doesn’t work if you have already installed the latest update. You need to unlock the bootloader for rooting if the you have that 62 firmware. Though other methods do exist, they are not for those who are new to rooting. DooMLoRD’s Easy Rooting Toolkit can also root devices from other manufacturers. Have a look at here for supported devices. If you want to claim warranty, you can always flash your phone using the official tool with the latest firmware.
I’m going to explain how you can root your Xperia phone even if you are already on the latest firmware (4.0.2.A.0.61 or 62 and up). You are going to downgrade your firmware in order to root your phone.
What you need to root your Xperia mobile:

An Xperia phone of course and the data cable
PC Companion
Wotan client (register for a free account) and its driver
Doomlord’s Easy Rooting Toolkit

Downgrading your Firmware:
1. Download Wotan client to somewhere on your PC.
2. Install USBFlashDriver.exe
3. Open WotanClient.exe and wait for it to finish updating its database.
4. Follow exactly what appears in the next window. There are 8 pointers for you to follow. For many of the Xperia phones, the service button is Volume Down.

5. In the next window, check Enable advanced settings.
6. Your model will be automatically selected. Select 4.0.2.A.0.58 firmware or lower.
7. In the CDA drop-down box select your region.

8. Enter your user ID and password and click Update. You will get one credit.
9. Click Next.

Wotan client will download the necessary files and flash your phone. On successful flash, Wotan client will ask you to disconnect the phone from PC and reboot. Now you have downgraded your firmware and you can root your phone without unlocking the bootloader.
Rooting your Xperia phone:
Before rooting, you need to install the ADB driver for your phone. On your phone, go to Settings>Applications>Development and enable USB debugging. Connect your phone to PC and wait for the ADB driver to install. Go to Device Manager on your PC and look for something like Sony Ericsson ##### ADB Interface Driver. If it’s not properly installed right-click the improperly installed device and install through Windows Update. The ADB driver should be installed now.

Extract DooMLoRD’s Easy Rooting Toolkit zip file to somewhere. ( The folder contains a folder and runme.bat.)
1. Click runme.bat. Ensure that you do what the window asks you to do.
2. Press any key on your keyboard.

In a moment, your phone will be rooted and rebooted. This method will automatically install Super User.
You can check for root status by installing Root Check Basic from the market.