VirtualBox Boot Guest VM from USB

Open Disk Management


Remember disk number see blue arrow ( i.e. It's PhysicalDrive1 )

Run command windows with Administrator

C:\Program Files\Oracle\VirtualBox>VBoxManage internalcommands createrawvmdk -filename "E:\Virtual Machine\VirtualBox\Ubuntu Xenial\usb.vmdk" -rawdisk \\.\PhysicalDrive1
RAW host disk access VMDK file E:\Virtual Machine\VirtualBox\Ubuntu Xenial\usb.vmdk created successfully.

Finally, open VirtualBox with Administrator