This little tutorial is for users, of AT&T ONLY, who unlocked their iPhones to work with 3rd party apps. If you have a bricked iPhone this tutorial will not work for you. To revert your firmware from version 1.1.1 (because you would rather have 3rd party apps. instead of the mobile iTunes Music Store) just follow these steps. I have confirmed that this tutorial does work, however, it is somewhat buggy and you may have a small heart attack or two. BE AWARE THIS IS MODDING YOUR PHONE – There is always the possibility of breaking your phone.

Things you must have – You must have an iPhone that is currently working on the AT&T network running firmware version 1.1.1

1) Download the iPhone1,1_1.0.2_1C28_Restore.ipsw from the Apple website. Link to file. For Mac users, do not unzip the file, leave it on your desktop and let iTunes deal with it later.

2) Dock your iPhone and connect it to your computer. Hold down the Home (Front) and Power (Top) buttons for appx. 10 seconds. Let the iPhone shut off. DON’T LET GO.

3) Release ONLY THE POWER BUTTON (Top). In appx. 10 seconds your computer will put the iPhone in restore mode. iTunes will now attempt to restore your iPhone. Once iTunes opens, you can let go of the Home button.

4) Hold down SHIFT key (Windows) or Option/ALT-key (Mac) when you click the Restore button. Select the .ZIP file you downloaded earlier.

5) Let the restore do it’s thing. There will be an error at the end, just ignore it.

6) At this point your iPhone should show a big yellow triangle and say “Connect to iTunes“.

7) Now you can run AppTapp to Jailbreak your phone. If you don’t have AppTapp you can download it here. AppTapp will restore your phone to a working 1.0.2 firmware even though it will be throwing errors along the way.

Run AppTapp again and install the Installer.app

9) AT&T Users Reset your iPhone before you start using the phone again. If you don’t you could incur charges from AT&T.

There you go, that’s how you downgrade. Enjoy having your Applications back.

(Find more tricks at http://www.myiphonetricks.com/)