Downgrade iOS 4.0 To iPhone OS 3.1.3 For Windows

This tutorial is for those who have decided to downgrade iOS 4.0 to iPhone OS 3.1.3 because of certain reasons, and I will separate the tutorial into 2 sections, which is downgrade iOS 4.0 to OS 3.1.3 for Mac and Windows. And in this post I will start the tutorial for Windows. So now let’s get started!

Note: For iPhone 3GS and iPod Touch 3G users: firstly to make the downgrading process successful your SHSH blobs (at Saurik’s server) must already been saved!

Now edit your HOSTS file and here are the steps to do so:

• Click Start->All Programs->Accessories and you will find Notepad, then right-click on it and select Run as Administrator
• After your Notepad opened then click on File at menu–> Open. Browse or navigate to C:\Windows\System32\drivers\etc click on HOSTS file.
• After the HOSTS file is opened, copy the following line and paste it at the end of file:
  

  74.208.10.249 gs.apple.com

  

• Back to File menu to Save it!.

Here is the second steps to downgraded your iDevice from iOS 4.0 to firmware 3.1.3.

1. You need iRecoveryWin32, so download the file here and then extract the zip file
2. Inside the iRecovery folder, you will “libusb-win32-filter-bin-0.1.12.1.exe” so run it and keep it on your desktop.
3. You need to turn iPhone off, then hold HOME and POWER button for 10 seconds.
4. Release the Power button after 10 seconds, but keep holding the HOME button until the message appears on your screen:
   
5. Hit OK. Now hold Option Shift+Restore button in iTunes and browse for 3.1.2 firmware.
6. And then you need to ignore the a message that will appear in a popup telling about error code 1015, remember ignore it!
7. Just close the popup by clicking OK also close iTunes
8. Go to command prompt and type the following command at the console
   

   cd Desktop iRecovery.exe-s setenv auto-boot true saveenv fsboot exit

9. Just sit back to wait for a little while, afterward disconnect iPhone from the cable
10. Press HOME and POWER buttons at the same time to restart your iPhone
11. You will see Apple logo on your screen in this phase, what you need to do is connecting your iPhone to PC via cable and proceed normally with the activation process.

Well done your iDevice has been successfully downgraded from iOS 4.0 to firmware 3.1.3

If you want to Jailbreak iOS 4.0 on iPhone 3G Or iPod Touch for Windows and Mac