I bought a leopard install disk a couple of days after leopard was released, unfortunately the computer store where I went was out of the retail boxes so I got a discounted "CPU Drop in DVD". I waited to install it for bug resolving sake. Now I tried to install it and after selecting my which language I rather install it in, I am told that the disk is only an upgrade disk and requires Mac OS 10.4 (or later), which cannot be found on my hard drive. Yet, I'm currently using 10.4.11. Could someone please tell me how to get my disk to recognize my OS or otherwise install Leopard?