So I bought my iphone 4 off a mate's mate, who had previously opened the iphone up to change covers etc. Anyways, my phone kept on switching off randomly and was pretty sure the battery was disconnecting. So when i opened it up I found the screw that holds the battery down was not there! To make things worse, the head of the screw has broken off but the rest is still in there.. Any ideas how i can remove it? I have a replacement screw itching to go in!