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 ...

Even if you’re a Windows fan, you’ve probably thought about trying OS X. Maybe you’d like to test drive OS X before switching to a Mac or building a Hackintosh, or maybe you just want to run that one ...