, Documents & Settings, (your user name), Application Data (if you cant see this folder make sure to go to tools folder options and make hidden files visible), Apple Computer, iTunes, iPhone Software Updates, and there's your firmware download, if you don't have a file here simply try to restore your phone and download the firmware from Apple. 2-Knowing how to get to your firmware from the step above, go into your iTunes and plug in your phone, make sure your phone is in recovery mode at this point, when in iTunes click restore and alt at the same time, look for the firmware (above) and open that file, it may fail the first few times but keep trying, it will install the firmware and your phone won't be blocked by Apple. **Make sure not to take your phone to Apple or AT&T because when they put your phone on the pc it will show a code, they will fix it for you but your warranty will be voided.