Originally Posted by
Watrat The instructions via the link you posted *should* be sufficient. Having said that, if you suspect that the installed iOS version may have gotten corrupted, you can have iTunes download and install a fresh copy of it. To do that, follow the instructions below.
1. Locate the .ipsw file on your computer and put it in the trash bin.
2. Put your device in
DFU mode. Note: Nothing will be displayed on your device's screen when in DFU mode.
3. After iTunes detects that the device is in recovery, select to restore and update it.
4. When the process is finished, you will be met with the Welcome screen. Proceed to set up your device from scratch.