If you have an older LabVIEW (6.1 or earlier) you will need to
exchange the in port and out port VIs that came with LabVIEW with
different ones and install a DLL. The reason is documented here
<http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/e6415e8a8376f63d86256c46007592e8?OpenDocument>.
This link (which is the first link returned when you search ni.com for
"in port") explains basically that the OS won't let you until you have
kernel level access. The devzone link at the bottom of the refered
page will include all of the code that you need to install (VIs and
DLL) to make it work.
