By 2021, virtualization software (like newer versions of QEMU, libvirt, and Virt-Manager) had moved heavily toward modern hardware emulation (PCIe, Q35 chipsets, UEFI). Windows 7 was not designed for this.
If you attempted to use QCOW2 for Windows 7 in 2021, you likely encountered the following feature landscape: windows 7qcow2 2021
If you have a Windows 7 install on VirtualBox (VDI) or VMware (VMDK), you can convert it in 2021 easily: By 2021, virtualization software (like newer versions of
qemu-img convert -f vmdk -O qcow2 windows7.vmdk windows7.qcow2
Then, use virt-rescue (from libguestfs-tools) to inject the VirtIO drivers before booting. Then, use virt-rescue (from libguestfs-tools ) to inject
# Inside Windows 7, run MSI from virtio-win ISO
# On host, add to QEMU command:
-chardev socket,path=/tmp/qga.sock,server=on,wait=off,id=qga0 \
-device virtio-serial \
-device virtserialport,chardev=qga0,name=org.qemu.guest_agent.0