The "Bootable" legacy ISO you've used is in fact not bootable, it relies on CDROM emulation provided by BIOS. VMs don't usually do this sort of emulation. If you set the guest OS to something like ...
How to create a VirtualBox virtual machine backup on a Linux host Your email has been sent Your data center might depend on virtual machines (VMs), and you might use VirtualBox for some of those VMs.