Speed: Skip the hour-long Windows installation process and boot directly into the OS.

Efficiency: QCOW2 supports snapshots and compression, making it easy to roll back changes.

Boot QEMU pointing to your Windows 10 ISO and the new QCOW2 file as the primary drive. Complete the installation as normal.

Create a blank QCOW2 file: qemu-img create -f qcow2 win10.qcow2 40G

Optimization: Most pre-made images come with VirtIO drivers pre-installed for better disk and network performance. Where to Download Windows 10 QCOW2 Files

Microsoft provides free virtual machines for testing purposes. While they are usually offered in VHDX, VMDK, or OVA formats, you can easily convert them.

The simplest way to update your QCOW2 image is to boot the virtual machine and use the built-in Windows Update utility: Start the VM in your hypervisor. Go to Settings > Update & Security > Windows Update. Click "Check for updates" and allow the process to finish.