background cutting

[Eliix]

How do i cut out the background in gimp? As in, cutting the black out around the girl in this picture: http://planetrenders.net/renders/albums/userpics/12707/normal_Carina%20-%20Pr.png

[CanadianBacon]

Because that render is a png, it should go away when you open it. It's usually there just to show people the render more properly.