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Xperia Arc/Arc S Update 4.0.2.A.0.58 (LT15i/a & LT18i/a)
Thanx to the XDA forum and Soul788and jlmcr87
it will work for both theLT15a/i & LT18a/i, it WON"T affect the 3G since its only software not hardware
http://forum.xda-developers.com/showthread.php?t=1330314
Make sure to download the second link it the above link (global generic)
or
http://forum.xda-developers.com/showthread.php?t=1357841
Solved! Go to Solution.
download FlashTool
http://forum.xda-developers.com/showthread.php?t=920746
or
http://androxyde.github.com/Flashtool/
Install it and you will see 5 folders
Custom
Drivers
Firmwares
Loaders
X10Flasher_lib
take the firmware to the "Firmwares" folder
click on Falsh
Press Ok
it will ask you to connect your phone on Flashmode (turn off your phone, press the back button, then connect the USB) press OK
This is an step by step guide
Make sure you backup everything
Settings -> privacy -> Back up my data and Automatic restore should be selected
and also
an even Easier alternative
download the app, transfer it to your SD card
Download Apk Manager
W251bGwsMSwxLDEsImNvbS5tYWdtYW1vYmlsZS5hcHAuYXBraW5zdGFsbGVyIl0.
open "Apk Manager" and voila select the apps that you wan't to install
Use one of these links to download the
Backup & Restore app
http://forum.xda-developers.com/showthread.php?t=1193802
or
http://www.elita-clan.com/downloads/backup_and_restore_v010935.apk
http://www.elita-clan.com/downloads/backup_and_restore_v010935.apkor
http://www.mediafire.com/?1n07llajeaoo03y
How to install it
You need to
go to settings -> applications -> check unknown sources
download IO File Manager
https://market.android.com/details?id=org.openintents.filemanager&feature=search_result
download the backup & restore app, transfer it to your SD card, use OI file manager to find it -> tap on it -> install it
Contacts
just to play it safe sync your contacts w/ google if you haven't already
open your phonebook
Don't worry so much about backing up your apps
on your computer go to
market.android.com -> log in -> click on My Library -> and send all your apps to your phone
SMS/MMS
if you don't want to use the backup & restore app then
Install "backup SMS" to back up your SMS and MMS to your Gmail
https://market.android.com/details?id=com.zegoggles.smssync&feature=search_result
or your SMS use
"backup & restore SMS"
https://market.android.com/details?id=com.riteshsahu.SMSBackupRestore&feature=search_result
or for your MMS use "Save MMS"
https://market.android.com/details?id=com.schwimmer.android.mmsextract&feature=search_result
Call Logs
And for call logs this is great
https://market.android.com/details?id=com.yang.android.ansta
download FlashTool
http://forum.xda-developers.com/showthread.php?t=920746
or
http://androxyde.github.com/Flashtool/
firmware
http://forum.xda-developers.com/showthread.php?t=1330314
http://forum.xda-developers.com/showthread.php?t=1357841
Install it and you will see 5 folders
Custom
Drivers
Firmwares
Loaders
X10Flasher_lib
take the firmware to the "Firmwares" folder
click on X10FlashTool (Application)
click on Falsh
Press Ok
it will ask you to connect your phone on Flashmode (turn off your phone, press the back button, then connect the USB) press OK
This is an step by step guide
5.a. Unplug your USB cable from the PCb. Power off your phone and plug the USB into the phone
c. Press back button and keep your finger on button
d. Plug USB cable into your PC whilst holding down the back button on your phone
e. A green LED will appear
f. The process will automatically detect your phone and start flashingg. When "Found at USB/........" appear on flash tool you may release"back button", sit down, relaxand wait.
Hope this is helpful to you
6. IF the "Start Flashing" message appear everything`s ok if not...repeat. Sitdown and relax (again )
7. When last message appear unplug/plug USB cable
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Regards,
Ricardo Rendeiro
__________________
what are the features of this update ??
Is this version applicable for the indian version of arc?
its flashing...so if you do that , your phone software will be either global or a country specific but not india 
I'm still testing battery life, so I'll let you know if I see any improvement
And whats with the wooden keyboard 
Can you flash this even if your bootloader is locked?