Two days ago I posted a link to an ipsw file that many used to upgrade their iPhones to the 2.0 software (I did as well). But, that version of the 2.0 software was actually meant for use on an iPhone 3G not on a first generation iPhone, you see iPhone 1,2 is actually a model number, a model numer for the iPhone 3G. The first generation iPhone has a model number of 1,1 so follow the steps below to downgrade to the official and supported version of firmware 2.0.

  1. Sync your iPhone with iTunes to make sure all your data is backed up.
  2. Download iPhone1,1_2.0_5A347_Restore.ipsw, you should get a single file but if your browser renames it to a .zip file simply rename it to “.ipsw”
  3. In iTunes click “Check for Updates” while holding the Option key (Shift key on Windows).
  4. Choose the firmware file downloaded from step two
  5. Wait about 15 minutes for your iPhone to be downgraded

Although I haven’t heard of any issues using the 3G version on a non-3G iPhone it is still a pretty good idea to go through this process and use the official non-3G version of firmware 2.0.

MacRumors