Downgrading iPhone Firmware
I see a lot of parallels between Apple's iPhone and Sony's PSP. Both add new firmwares like crazy to their devices in an effort to keep device hackers at bay. Apple recently upgraded the iPhone's firmware to version 1.1.1 which made many modified iPhones inoperable.
The major annoyance is most likely the fact that users can't add third party applications to their iPhone anymore which is in my opinion a major mistake by Apple. The community is always creative no matter if the product is a PSP, an iPhone or an Nintendo DS. They create so many useful applications that people will stick with the device no matter what.
I do not own an iPhone and have no intention to buy one. I'm perfectly happy with my Nokia N73 which allows me to install any applications that I would like. (supported ones only of course.) I nevertheless thought it would be good for all iPhone users to copy and paste the instructions on how to downgrade the iPhone firmware from version 1.1.1 to 1.0.2.
1.0.2. is the one that can be modified.
Downgrading iPhone Firmware Instructions:
1. First, download the iPhone1,1_1.0.2_1C28_Restore.ipsw from Apple. On a Mac, do not unzip the file, iTunes will do this for you in step 4.
2. Then connect phone to dock, and hold down home button and power button for about 10 seconds or until the screen goes black.
3. Now release the power button but continue holding the home button. After about 10 seconds the computer will detect the iPhone in restore mode, and iTunes should tell that the phone needs to be restored.
4. Hold down SHIFT key (Windows) or Option/ALT-key (Mac) when clicking the Restore button, and select the file you downloaded in step 1.
5. Let the restore complete and ignore the error at the end. (Should be error 1013).
6. Now your phone should show the "Connect to iTunes" screen with the yellow triangle.
7. Run AppTap to jailbreak your phone - it will restore it to a working 1.0.2 firmware it even though you will get an error at the end. Just dismiss the error and quit the installer.
8. Run AppTap again to actually install the installer.app. It should successfully complete. Keep rerunning AppTap if it doesn't work the first time - it may take a few tries.
9. At this point you will have a jailbroken iPhone that still needs to be activated (as usual). Google is your friend.
10. AT&T Users: Reset your iPhone before you start using your phone again. Failure to do so may result in you being charged for your "free services."