Ok sean do you know or use the Windows AIK or ADK ( ADK is the latest version ) - this allows you to edit the unattend.xml -
There is another way you could do it and that is by adding a runonce command to your actual image registry.. before you capture it. So on first logon the image itself will run the command.
cmd /c %systemdrive%\ldprovisioning\ldprovisioning.cmd
If you are not familiar with the AIK or ADK and dont need to customise your install any further the runonce option will be the quickest test.