: Use tools like Disk2VHD from Microsoft on your physical Windows 7 machine to create a VHDX image. Then convert this to QCOW2 using qemu-img :

A QCOW2 file only occupies the space actually used by the guest OS. Even if you allocate a 100GB drive, the initial file might only be 8GB.

Open Virt-Manager and select "Import existing disk image."

qemu-system-x86_64 -m 2048 -drive file=win7.qcow2,cache=writeback,if=virtio,boot=on -cdrom virtio-win-0.1-81.iso -net nic,model=virtio -net user -boot order=c -usbdevice tablet --enable-kvm

The Ultimate Guide to Windows 7 QCOW2 Images: Creation, Deployment, and Optimization