hi there, i was given an iphone because a friend upgraded and i have no idea how to use it. it came up with a low battery logo so i plugged it into my macbook to charge and it then launches the apple logo and freezes after the little circle loading thing goes round once. it then stays like that for 5-10 minutes and goes white, then back to the apple screen and repeats. it doesn't show up in my itunes. i don't have a sim card in it at the minute, could that be a cause?? i also hear but dont know how to test that she believes the home button doesnt work, or doesnt work well. what on earth am i to do to fix this? i'm a total newbie to iphones so any help would be greatfully recieved. thanks a lot for reading!