Can I transfer boot sector to a non-bootable image file and make it bootable?

I have a CD image file that is supposed to be bootable, but it's not working. I have checked the checksum and I never burned it to physical media, I'm using it in VirtualBox. So the download is OK.

I googled and found this method:

http://bootableusb.net/make-non-boot...mage-bootable/

It's a Windows application. It even runs on Wine, but it's a paid program and I want to have it done for free. Can Linux do it?

TIA