This issue is most likely caused by the fact that the VNC Mirror Driver has only been partially installed.
Please navigate to Control Panel > Device Manager and check for any devices listed as "Unknown Device". This will most likely be under "Display adapters" but could equally be under any of the drop-downs contained in this window.
Once you find the "Unknown Device", right-click on it and select "Uninstall".
You should now be able to reinstall VNC Server and the Mirror Driver without issue.