When you press the Delete button on the Administration|Organisation screen, a confirmation window will appear.

If the selected Organisation is not in use and can be deleted, the window will simply ask you to confirm the delete. Press OK to confirm or Cancel to abort.

If it cannot be deleted because it is in use, the text will be "xxxx has relationships and cannot be deleted. Do you want to deactivate it instead?"(where xxx is the name of the item you are trying to delete). Pressing OK will unset its Active flag, Cancel will abort.

If it is in use but can be deleted, the text will be "xxxx has relationships. Are you sure want to delete? This operation cannot be undone." (where xxx is the name of the item you are trying to delete). Pressing OK will delete the item as well as all references to it, Cancel will abort.