>From what you describe, I would surmise that the main problem is that you use BIOS instead of UEFI to boot your Windows image: if it is not already installed, install the ovmf package and invoke KVM with the needed parameters. There is an ovmf page in the Ubuntu wiki: https://wiki.ubuntu.com/UEFI/OVMF
Disclaimer: I have never imported Windows pre-existing images and I do not use QEMU/KVM directly, only through the virt-manager GUI
