Hey try this -
1.download latest flashtools which is a program that you would be using as long a you want to flash custom rom from here: http://androxyde.github.com/Flashtool/
2. Now in the Flashtools folder (C:\Flashtool\firmwares by default) go to the folder named drivers and you would see "flashtool-drivers" and install them (installed them all just in-case you decide to get another Xperia phone in the future.
3. On your phone go to setting>applacations>unknown sources and usb debugging in development and connect your phone to your computer with your data cable and then open flashtools.
4. root would now become available in flashtools so press it(the black unlocked lock ICON) and just wait for flashtools to reboot your phone. and you now have root access!
Installing a Recovery
In order to install a new Rom you would have to install a Recovery, according to the rom you want to install the thread would state whether you need a ClockWorkMod(CWM)(CWM5 in flashtools) or just flash through Xrecovery(0.3 in flashtools)
So in order to install a Recovery your phone must be connected to the USB port on your computer. So in flashtools click on the black square with a white cross in it and choose according.( setting>applacations>unknown sources and usb debugging in development much be on.
How to use Xrecovery.
To get into xrecovery you much power off your device, then press the power button until it vibrates, no when you see the sonyericsson logo start pressing the back button on your phone and then you would enter Xrecovery(in the version of flashtools this tutorial is based you must wait until you see the notification LED turns ) now in xrecovery you use the volume up, down, home and back buttons to navigate.
5.unplug your phone and power it off. On the top bar in flashtools plugins should now be available with the "Unlocked bootloader" option, so press it and wait until it says to connect your phone then do so by holding down your back button(on your phone) and plugging in your USB cable(don't let go until you see your notifications light come on GREEN
6. While the unlocking is taking place look out for the "you can now unplug and turn on device, then plug it again" unplug it and press the power button until vibrate and then Immediately plug it back in. Do it that one time and just leave it to finish and say "successfully applied unlock. Rebooting
7. Smile because you can now flash custom kernels and so forth and so on and also press thanks button.
If your stuck just send me a message.
Quick tip:flashing new roms usually means loosing your data(contacts, apps, etc) but you can use this to backup your data and when you're done re-download it and restore your data: https://play.google.com/store/apps/d....go.backup.pro
for more visit this thread http://forum.xda-developers.com/show....php?t=1821750