under chuck norrises bed. yea, even hes scared of me
go to www.planetrenders.net and sign up for the RENDERS section (theres different sign ups for forum and renders on there!) and then when you save a render it will have a transparent backgruond when moved into photoshop. so there its fixed!
Most people think that once they render an image they can just slap it on any old colour background, but then you have to re-render it which just completely defeats the object of rendering it in the first place. All renders should be saved as PNG files and slapped onto a transparent background.