Jailbreak (unlock operating system) iOS 4 of iPhone 3G, 3GS and iPod touch 2G

Jailbreak (unlock operating system) iOS 4 of iPhone 3G, 3GS and iPod touch 2G. Know how to Jailbreak iPhone 3G, 3GS, iPod touch 2G running on iOS 4 with PwnageTool 4.0

Steps to Jailbreak iPhone 3G, 3GS, iPod touch 2G running on iOS 4:

• Download and install the latest version of iTunes >> iTunes 9.2
• Run iTunes and sync your iPhone with PC so backup important data
• Download PwnageTool 4.0, and iOS 4.0 for your iPhone or iPod touch version
• Start PwnageTool 4.0 and select your device

PwnageTool 4.0 will now automatically detect the suitable firmware for your device (check out below screenshot)

When PwnageTool asks you “Do you have an iPhone contract that would activate normally through iTunes?”, click on “NO”. Clicking on “Yes” will update your baseband to the latest version. Click on “Yes” only if you are on an officially supported carrier like AT&T.

PwnageTool will now create the custom .ipsw file for your iPhone which will be jailbroken

Once the .ipsw file has been created successfully, you will see “ihaz Success” screen like below:

Now you have to restore your iPhone to this custom firmware 4.0 that you just created using PwnageTool 4.0 for your iPhone or iPod touch. Click on your phone icon from the sidebar in iTunes. Now press and hold left “alt” button (“Shift” button on Windows) on the keyboard and then click on “Restore” (Not “Update” or “Check for Update”) button in the iTunes and then release the “Shift” button. This will make iTunes prompt you to select the location for your downloaded custom firmware 4.0. Select that custom .ipsw file and click on “Open”. Now sit back and enjoy as iTunes does the rest for you. This will involve a series of automated steps. Be patient at this stage and don’t do anything silly. Just wait while iTunes installs the new firmware 4.0 on your iPhone. Your iPhone screen at this point will be showing a progress bar indicating installation progress. After the installation is done, iPhone will restart automatically and you should now have a fully jailbroken iPhone running on iOS 4. You are done.

After jailbreaking your iDevice with PwnageTool 4.0, you can now unlock it using Ultrasn0w 0.93. [source - Redmondpie]