don't unpack the ISO. Nero will burn the iso image file. Just open nero and when the new compilation box appears just click "open" and select the iso then burn.
A better way of burning (because many people have problems burning with nero and to be honest it isn't very reliable), just download the free burning tool IMGBURN then you can just open the iso and burn. Its a much better burner than nero and the discs are much more compatible than any i have burned using nero