This commands removes a hard disk, DVD or floppy image from a VirtualBox media registry.[38]
VBoxManage closemedium [disk|dvd|floppy] <uuid|filename>
[--delete]
Optionally, you can request that the image be deleted. You will get appropriate diagnostics that the deletion failed, however the image will become unregistered in any case.
[38] Before VirtualBox 4.0, it was necessary to call VBoxManage openmedium before a medium could be attached to a virtual machine; that call "registered" the medium with the global VirtualBox media registry. With VirtualBox 4.0 this is no longer necessary; media are added to media registries automatically. The "closemedium" call has been retained, however, to allow for explicitly removing a medium from a registry.