iTunes can sometimes get on your nerves displaying confusing error messages without providing proper explanation even when help button is clicked, something similar occurred when my iPod firmware got corrupted and I used the Restore function in iTunes but to my surprise iTunes displayed error - "The iPod BNB could not be restored because the firmware file could not be found." , I allowed iTunes to check internet for firmware download but the error persisted.
This issue is caused when you have firmware files already downloaded in iTunes cache location but it gets corrupted, instead of allowing you to download a fresh copy of the firmware our not so smart iTunes keeps showing this error, to fix the error simply follow the solution next.
- Open Windows Explorer and type %APPDATA% and press enter in address-bar, this should open current users Application Data folder.
- Now navigate to Apple Computer -> iTunes folder.
- This folder should contain a folder named - iPod Software Updates simply delete it or rename it.
- Launch iTunes and click restore button, it will now ask you to download the firmware file and everything should work fine now.