The files on the DVD don't look bootable.. In order to rule out that it's not an issue with that physical computer and in order for the thing to be reproducable, i thought of trying it in a Virtual ...

Here's how to change the boot order of a guest OS in VirtualBox. It is indeed possible to set up your guest OS to boot from CD/DVD-ROM, HDD or network (as long as these features are supported).

The virtual machine may fail to boot from an ISO because the boot order prioritizes the virtual hard disk over the optical drive, resulting in a “No bootable medium ...