Hello,
The link below to the driver information page works, but the link to the driver itself is an external link, likely to the manufacturer website, which indeed seems to be broken. This would be a good thing to send and note to instrument.drivers@ni.com as they will likely be interested in fixing it. However, the minumum version of LabVIEW that the driver works with (as noted in the page linked below) is LabVIEW 6.0, and you note that you are using LabVIEW 5.1, so a fixed linked may still not be useful to you.
Link: http://sine.ni.com/apps/we/niid_web_display.download_page?p_id_guid=E3B19B3E9737659CE034080020E74861
Repost if you have any other questions!
Best Regards,
JLS