A empty world for make icon?

hello everyone,
i wish u can help me… Im almost new in blender;-) I wanna create a icon for the desktop and after modelling my mesh i wanna make the color of the world empty that when i rendering i can see just the object…like a icon;-)
sorry for my english pretty bad;-)
Anyway thanx

Im sorry see now that i misteke place to post:-( sorry, sorry, sorry…

To make the background transparent all you have to do is to enable RGBA rendering instead of RGB by default. The button is in the render options tab.