How to:Downgrade iOS 4.0.2 to 4.0.1 for iPhone 4/3GS/3G And iPod Touch 3G

As we all know that Apple has just released the new version of iOS 4.0.2, but for all those who are not satisfied, or want to downgrade to a pervious version of firmware can follow the guide below.

Important Note:

iPhone 3G users can downgrade using the following guide. iPhone 3GS/4 and iPod Touch 3G usersmust have to ECID with SHSH. Saurik saved in the serverand modify the hosts file in order to succeed in the procedure see below:

Requirements:
-The latest version of iTunes.
-The original firmware which you intend to downgrade to it from here.
-iRecovery and libusb for Mac or EasyiRecovery for Windows.

Modifying the hosts file:
For Windows:
-Open Notepad with Adiminstrative privilages, click on Start > All programs > Accessories then right click on Notepad then select open as Administrator.
-Now browse (C:/Windows / System32 / drivers / etc) in the Notpad and open the hosts file then add the following line at the end of the document and save it:

74.208.10.249 gs.apple.com

For Mac:
-Click "Go" -> "Go to Folder" and enter the path / etc /
-Find the file "hosts" and move it to your Desktop.Open the file by right click then open with Text Edit and add this string at the end:

74.208.10.249 gs.apple.com

-Save the file to your desktop and then drag it back into / etc / . We will request permission to overwrite and then also the administrator password.