Here is some information out of the 6.1 readme file that should help you out. You can find the rest of the readme file at the following page:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/86256a47004e16d186256b1b00542948?OpenDocument
If while installing LabVIEW on Windows NT/XP you encounter a "1923. Service 'NILM License manager' could not be installed" error or a "1920. Service 'NILM License manager' failed to start" error, select the "Ignore" option and let the installation complete. After installation, place double quotation
marks ("...") around the value of ImagePath in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NILM License Manager.