Ya I had a OSX Leopard CD that i used to try and clone my HDD, the disk utility on Leopard seemed to have issues and would not work. You can try booting ur computer into target disk mode by holding "t" on startup and then connect ur imac to another imac and see if the HD comes up, this will allow you to format the HD using the other iMacs Disk Utility. You can also try and use a Snow Leopard CD if you know anyone with one.