iPhone 4 software update problem

I have been trying to update my iPhone 4 software update for more than six hours. I did the update through my phone instead of plugging it in, and it is stuck at the end of the update. The screen has the apple and the bar across it with the bar stopped at the very end. I tried restarting the phone, and it restarts then goes back to doing the update and freezes again. I also tried plugging it in to iTunes, but because my phone has a passcode, it won't let me into anything, because I can't type in my passcode. Can anyone please help?