Iphone 4 screen replacement screw stripped?

Like most people I dropped my phone and unfortunately when I went to pick it up there was a huge spiderweb crack all over the screen.

Using http://www.ifixit.com/...ly/11755/2 I started to disassemble my iphone to replace the screen after I received the repair kit.

When I reached Step 12 (see link) I noticed the screw was completely stripped (this is the first time I opened it and it was stripped when I lifted the dock cable.

How can I remove the stripped screw (cheaply) without damaging the Iphone so I can replace my screen. Is there any way I can reuse the screw afterwards or is there a place that would sell me these screws

Added (1). I got the iphone from apple (supposedly) new

You can't. And that screw being stripped BEFORE you touched it tells me whoever owned the phone before you tampered with it.