If the 3D dock  of Mac OSX Leopard is not to your liking and you do not know how to modify it, here is an application to customize the dock as you wish : Superdocker.       Well, search free applications for Mac is not all the time easy, but Superdocker is totally free and has many various features.  

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Yay for Super Docker. I've been using it for a few months now and it works great. I love it.