How To Change Your Mac Log In Screen (Mac OS Leopard)

First, open the finder. Then go to HD --> System --> Library --> CoreServices and find the DefaultDesktop.jpg.

(Click the Image To Get a Larger View)

Ok that's the image you need to replace with your custom image. Before replacing the image, you need to change your image's name to DefaultDesktop and the image format to .jpg. That's it. It's all what you need to do and enjoy your custom log in screen.