Can't boot a virtual machine

I made a true image backup of my C drive before I zapped my machine to do a clean Windows 7 install. I then converted the True Image backup to a virtual disk. When I try to run this as a virtual machine in Windows 7 it won't boot because I'd previously been using a boot manager to select which partition I wanted to boot. I'd forgotten all about this as more and more I'd just used the Vista 64 partition and thought only of that. Is there a way I can force this to virtual disk to become bootable?

The specific failure message is

BOOTMGR is missing
Press Ctrl+Alt+del to restart

Thanks for any help that cna be provided.