For a while this was not available through iTunes, but I did this today after finding a thread on ModMyi: http://modmyi.com/forums/other-methods/727994-i-may-sound-unbelievable.html.
I hope this helps someone. I needed to downgrade a friend's 3G to jailbreak and it worked. Just use the Alt-Click method and choose 4.0.1.
I hope this helps someone. I needed to downgrade a friend's 3G to jailbreak and it worked. Just use the Alt-Click method and choose 4.0.1.