Windows NT is not a PnP OS, and unfortunately installing ISA PnP boards on this OS can be tricky. For some troubleshooting suggestions, I would suggest that you visit:
http://www.ni.com/support/daq/winnt/pnp/pnt.htm
This troubleshooting wizard will give you some helpful hints on what to check for if NT is not detecting your board.
Hope this helps! Otherwise, I would recommend visiting ni.com/ask for technical support.
Regards,
Erin