This iPhone has only been used as an iPod Touch since I've long upgraded. It's been sitting around for a while, the battery had completely drained, and now it won't work at all. It's continually in DFU mode with the error code 2001, which I looked up on Apple.com and it's pretty ambiguous. Nothing I do can get this phone to restore itself. It's never been jailbroken or anything either. Any help?