Dennis is right. On the other hand, we could also assume that you are using NI's PCI-GPIB, but you are using a different driver version, such as v1.7. The GPIB-USB-HS is only supported by v2.3, so there would be the conflict in the DLLs. The option here would be to strip out the dependency of the DLL in your program, so that it is purely the driver's API calls, just the user-level application. Then, you could install the v2.3 driver to use with the GPIB-USB-HS.