My iPhone 4 won't turn on and when I try to restore I get error 21?

I dropped my iPhone yesterday and it shut off like it does sometime, I plugged it in and it worked right away like always. Well last night it was off so I figured it died until I plugged it in and it was only showing the Apple icon. I plugged in into iTunes like it said and I tried to restore it. Everything seemed to be fine but then it said it couldn't restore and gave me error 21. I don't know what to do and I don't want to go out and buy a new one. Is there any chance of me fixing this?

Added (1). My insurance claim would be the same price as a new iPhone, and my phone is not jailbroken

Well do you pay insurance and 2. Try the apple store, I actually never heard of that error. But if its jailbroken than your screwed same thing happen to me, but it was a software problem and never turnt on.