Dough,
Like any other evaluation software from any company you would download and install, after the evaluation period is expired there is no way to reinstall it and have it back and running again (except for reinstalling the OS). Otherwise people wouldn't need to buy software and just keep and running evaluation versions.
Regards,
Cyril Bouton
Applications Engineer
National Instrument
Cyril Bouton
Active LabVIEW Developper