[Sony Xperia S, Acro S, Ion] chrissiong:
For windows 8.1, you will need to use another method to install the necessary drivers for your computer to detect the devices in flashmode and fastboot mode. I dont know it is working or not because i dont own windows 8.1 computer:eek:

First of all, the files you will need to proceed next step

1. flashtool. you can download it in offical website http://www.flashtool.net/download.php

2. original ftf file of xperia sl (credits to ska67) http://xdaforums.com/showthread.php?t=2423025 Just download all parts and extract it together to get the whole ftf file

3. usb cable

If you prepared those files, lets get started:cool:

1. install the flashtool(this is necessary because we need it flash the ftf)

2. copy the ftf file to firmwares folder (flashtool>firmwares)

3. for the drivers, the setup.exe is located in flashtool folder (flashtool>drivers>setup.exe). AFAIK, you cannot install the drivers directly in windows 8.1, you will encounter error messages while installing

To successfully run the drivers installation, you need to follow these steps

1. Update your windows 8.1, the files can be download in this website http://support.microsoft.com/kb/2917929, if you are on windows 8, just skip to step 2

2. Once you are done, follow this tutorial(credits to neroyoung) http://xdaforums.com/showthread.php?t=2095087

3. If you follow the steps correctly, now you should be able to install the drivers without getting error:)

4. Install the drivers(i already told you the file location at above)

5. Remember when you start the installation, check the box of the flashmode and fastboot drivers and install

6. Once the installation done, restart your computer

7. After this, now your computer should be ready for the flashtool to work:D

Now, this part is for the ftf installation

1. Power off your phone (just leave it beside, we need it afterwards:))

2. Run the flashtool

3. Click the thunder icon (choose flashmode and click OK)

4. A window will prompt out, click the firmware of your device, i assume that you have placed the ftf file inside the firmware folder(it should be named as LT26ii xperia SL, the version will be 6.2.B.1.96)

5. For the options beside it, just leave it there (for the misc section, check the box named with no final verification)

6. Now, you can click the flash button(you need to wait for awhile before a window prompt out

7. A window should be prompt out telling you to connect your device to the computer.

8. Take your phone, press and hold the volume down key

9. Keep it pressed, connect the usb cable to your pc

10. release the key once GREEN LED lights up

11. Now the flashtool will start flashing, let it finish to 100%

12. In the meantime, DO NOT UNPLUG OR PLAY WITH YOUR PHONE BEFORE IT REACHES 100%, YOU WILL RISK BRICKING YOUR PHONE IF THE INSTALLATION WENT FAILURE

13. Once it reaches 100%, it should tell you to disconnect your phone and power on

14. the first boot will take a few minutes so patiently wait for it

15. once its done, have fun with your phone:D

PS: Follow the steps and be careful, I am not responsible if you brick your phone, burn your house or blow your PC by following this guide.

As i just say from the start, i do not own a windows 8.1 computer and i cannot confirm this tutorial is working or not;)