When a driver uses VISA for instrument connectivity, your GPIB card must be supported by a VISA library from any vendor. For example, NI GPIB is supported by NI-VISA, Agilent GPIB or HP-IB is supported by Agilent VISA. Some 3rd party GPIB products may be supported by NI-VISA through the replacement GPIB-32.DLL or through the NI-VISA passport plug-in. If your IOtech GPIB is not supported by any VISA library, it can't be used with instrumenr drivers as is. To solve it, 1)you need replace your GPIB with a VISA-compatible card, or 2)Modify instrumet IO portion of instrument driver to fit with the GPIB card you use if driver source codes are available. Normally IVI-C and LabVIEW Plug&Play drivers come with source codes.