guys, need some help please. i was messing with a friend's jailbroken iPhone, i needed it in dfu mode to restore it but i probably did something wrong because phone is stuck with a blank screen and nothing can make iTunes recognize it. it's an unlocked iPhone 4 running a jb 5.0.0 iOS. i really can't get it to boot no matter what. it doesn't even show under usb devices currently connected. i left it connected to the wall charger -i read somewhere that while in dfu mode, phone isn't really charged, but someone said it helped somehow- without any success. i'd prefer not to have apple service it because i guess they can boot it and see it has been jb. thanks.