NI-VISA only works with NI GPIB boards and some HP GPIB boards. You would have to install a VISA driver from your GPIB card manufacturer. NI Knowledgebase 20KCIS7Z at http://digital.ni.com/public.nsf/websearch/E56D3D4866BE0A8A86256942006626F0?OpenDocument has more information on the issue.