Need help using a render

[Denial]

I'm trying to make a sig out of this render: http://planetrenders.net/renders/displayimage.php?pos=-29695

I can't seem to cut out the image without taking the background with it too, i've tried the wand and everything. (i'm using gimp) it's annoying the hell out of me, any help?

Edit: don't worry, figured it out.