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 ...
Passcape ISO Burner is free portable software for Windows that lets you easily burn ISO image files to CD/DVD/USB. It also lets you create bootable disks or a bootable USB drive from the ISO images ...