"Disk.info" should be in the root directory of any disk.....
He mans the white rectangular hard disk icon. It could be anywhere on the disk, it might even be created via some C command used in the install / prep hd scripts.
A disk icon should always be named Disk.info and reside in the root of the disk in question. It can contain any image you want. So if you have an icon resembling a hard disk, you can rename it to Disk.info, make sure its type is DISK, and put it in the root of the volume. Then it should display on your next boot.
If you don't have any Disk.info in the root of a disk, it will (normally) just use the default floppy icon. (Under OS4, there are some extra defaulting mechanisms, so you can assign a deficon based on the device name etc., but that's not relevant here.)
Best regards,
Niels