How restore a non working windows partition and how install a proper bootloader.
2011/01/install-burgbrand-new- universal-loader-from-grub-in- ubuntu/
2010/11/how-to-manually- repair-windows-7-boot-loader- problems/
showthread.php?t=1014708 How to restore the Ubuntu/XP/Vista/7 bootloader (Updated for Ubuntu 10.10)
Convert virtualbox .vdi to physical & bootable second diskActually this is very simple to accomplish. As stated before you need to unload all the drivers off of the virtual machine. get it back to the standard default drivers that came with it when you first installed the OS. This can be done a few ways but the easiest would be with sysprep (otherwise you an manually uninstall them all... never tried it this way but I suppose that it could work).
After you get it back to the factory defaults it is as simple as cloning the HDD via a program that you can boot into. My personal favourite is Hiren boot CD. I use the Norton Ghost utility off it to create a clone of the virtual HDD onto a DVD. This is accomplished by booting the virtual machine up with the Hiren CD.
With that DVD then I can boot up the physical machine with Hiren go to the Norton Ghost program and then reverse the process uploading the new image off of the DVD onto the HDD.
Overall this process takes about a hour, of course depending on the size of the virtual machine and the speed of the PC that you are using.