How to change your firmware (Sony Xperia Go)

The most basic thing are:

1. flash tool  software (after you installed it, it will opened just like picture below)..

download through this link -----> http://www.4shared.com/file/ByOxNqzM/flashtool-0980-windows.html

 2. Follow the instructions from this link----> http://xperiafirmware.com/8-firmware/22-sony-xperia-go-st27

from this link, there are 6 guidelines to:-

1. how to install the newest Android 2.3.7 for your phone (for Sony XPERIA Go ST27i it is currently the 6.0.B.3.184 firmware)
2. how to install the newest Android 4.0.4 for your phone (for Sony XPERIA Go ST27i it is currently the 6.1.1.B.1.54 firmware)
3. how to install the newest Android 4.1.2 for your phone (for Sony XPERIA Go ST27i it is currently the 6.2.A.1.100 firmware)  
4. how to backup your original firmware customization (it is important in case you must send your phone to service) 
5. how to unlock the bootloader (in case you want to install the custom kernels with recovery menu and much more) 
6. how to relock the bootloader (in case you want to go back to stock (original) ROM or you must send your phone to service)

The firmware for any type of Sony Xperia other than Xperia Go can be found on this link too...
and still using the flash tool software.

There is no harm to the phone as long as you not try to root it yourself.
This is just the way to "upgrade your phone's firmware"...  

The other way to upgrade your phone's firmware is through Sony PC Companion...

Gud luck...!!!!!   :D