The screenshot indicates that the partition marked as active is the Recovery partition. On MBR disks, there can only be zero or one active partition, and if one exists, that is the partition the system will attempt to boot from when booting from that disk. If there are zero active partitions, then the disk is deemed non-bootable. I suspect if you marked the Windows partition as active in your first scenario — which can be done from Reflect Rescue Media, booted from an ISO within the VM — it would start booting even without the Recovery partition, but it definitely will NOT work with no partition marked as active. This isn’t specific to viBoot. It’s just how Legacy BIOS booting and MBR disks work.