ok, u got 4.0.4 ICS Pro with 4.1.A.0.431 and u wish to upgrade to .587 ICS. u plug in pc, using SPC (sony pc companion), u update ur PRO without clearing off the unit's data and setting. and wtf u end up with a clean ICS without root.

Before starting anything, u should have:
- Flashtool
- ADB driver installed for a working flashmode for ur PRO
- download this Rooting toolkit

so what u need to do is....

1. Go to settings > Security > Mark  "Unknown sources"

2. Settings > Developer options > Mark USB debugging

3. Settings > Xperia > connectivity > USB connection mode > select MSC mode

4. Uninstall 'superuser' app from ur PRO (which u had it last time in ur previous firmware).

5. Download this kernel and also this kernel. put them in the C:/ Drive > flashtool > firmwares

6. via Flashtool, enter flashmode, and select kernel MT11i kernel and ok. your PRO will definitely end up blackout. do not worry as it is normal.

7. take out the battery, wait for 5 seconds then plug back the battery and ON it. there will be a vibrate on startup and a 2nd soft vibrate on login. connect it to the PC via usb cable. A properly startup PRO can be detected by either the 'removable drive' in 'my computer OR SPC detection OR to-do pop up.

8. open Rooting toolkit folder, select 'run.bat' and follow instructions on the command screen.

9. once finish, unplug cable off. take off the battery of ur PRO, wait for 5 seconds, plug it back.

10. Open flashtool again, enter flashmode, select MK16i kernel and ok.

After that, restart ur PRO and check if superuser is back or not. I assume it is rooted and only rooted.

siuyi will look for a shortcut to install CWM next. have faith~

credits to nabeel and doomlord
sos

1. download this and extract it on ur desktop.

2. connect ur PRO to the pc. set is screen sleep more than 1 min.

3. Double click 'SE_Extreme_Tweak_Installer.exe' and select from the list for 'CWM for xxx/xxx/PRO/xxx, then click 'Install'

4. once finished, restart ur PRO, then spam the volume - button when SONY logo got brighter (u know what im talking if u used to have CWM in ur PRO). if u are able to enter the CWM mode, then u r good to go.

credits to quangnhut123
sos *i re-upload the .rar coz the original had become a broken link in the sos.