If you get the error message
"<b>Error starting domain: Requested operation is not valid: network 'default' is not active</b>",
then try to start the default virtual network:

<span class="command-placeholder">size</span> has to be at least `7200M`.

Click on **Boot Options** in the left pane.

The video device that provides optimal graphics performance can be different depending on the version of the host operating system.

Start with *Virtio* and *QXL* video devices: they generally give
the best results. If they don't perform well for you, try every
other video device model.