How to create a bootable hard disk image from an iso image?

I would like install a proprietary operating system onto my CentOS box using VirtualBox. There is a problem though, when I mount the install ISO image as a DVD, soon the installer complains of missing DVD drivers. I tried to download some but they did not work. Now I want to circumvent the DVD issue and I would like to create a virtual disk image of the install ISO. The forum discussion [ISO To VDI VBoxManage convertfromraw Not Bootable](https://forums.virtualbox.org/viewtopic.php?f=1&t=37765) says that >I am trying to make a bootable vdi from a bootable ISO >for linux guest. I am running >VBoxManage convertfromraw source.iso output.vdi >I get a valid vdi that I can attach and read but I cannot boot from it. Any idea how to solve this. for an experienced forum user says >To use "convertfromraw" your starting point (as the name implies) has to be a raw image of a hard disk - which an ISO image most certainly is not. In spite of this, is there a Unix way of creating a bootable hard disk image of a Windows 7 install disk? And, to create a .vdi file of that?