A disk that is installed in my Mac does not appear in the Drive Setup window, so I can't initialize or partition it.
This occurs when a disk is not installed properly, is not compatible with the bus to which it is attached, or the disk itself is defective. It can also occur with some disks that are not compatible with Apple's Drive Setup application.
If you have never used the disk before, it is possible that the disk is not installed properly.
If you installed the “missing” disk yourself, open up your Mac and check the physical installation of the disk. Ensure that it is properly connected to the correct bus. You also need to make sure that the disk is the correct format ...