If you are using XPERIA X8 or W8, here is a guide for rooting the stock Android 2.1 system and any official update version. I think the Sony Ericsson default user interface is beautiful, but it is too slow, because there is a lot of applications running in background, many of them is the Sony Ericsson stock applications and these things can not be delete except you root XPERIA X8. Furthermore, you can install custom roms after rooting the phone.
OK, Let’s begin rooting X8, you need a PC connected to Internet, the phone data cable and battery level of your X8 is above 60%. Now active the phone, press menu key, tap settings, tap application settings, tap develop, check the USB debug option. Connect the phone with data cable. If it is the first time that your X8 connect to the computer, in the USB mode menu, you should choose “install PC companion”, then your computer should remind you found usb device, and start download and install the latest Sony Ericsson PC Companion software.
Make sure the pc companion is installed correctly, then download the SuperOneClick tool, you can get the latest version from the original thread, unzip it.
Now disconnect the usb, then connect the X8 with usb again, pay attention, DO NOT CHOOSE ANY THING ON THE PHONE, leave it alone, now run the SuperOneClick tool, the green Android exe file, click the big “Root” button, now wait for a few minutes, it will tell you successfull root your X8. Now disconnect the usb connection, reboot X8, now you get your XPERIA X8 rooted. you should see the super permission icon shows in your app drawer. Any operations which need root permission will show a warning tips.
As XPERIA W8 has the same hardware with XPERIA X8, to root XPERIA W8, just do the same operation.
[update 5/6/2012] gg-driver for windows, fix * daemon not running. starting it now on port 5037 * and other stuck errors. download link : http://www.mediafire.com/?10mg9e5s2pn3j7q