This ExtIO DLL requires HackRF.dll
Issue: Unfortunately the only place to get this DLL is part of an existing package, and those only have 64bit versions of the DLL, There's no publicly compiled copy of the 32bit version of the DLL anywhere on the internet available for download that I could find. However there is source code that could be compiled into 32bit mode by a person with skills at compiling source code (I always have trouble getting C or C++ to compile anything, so I'm not about to do this).
Solution: You should compile the required HackRF.dll (a direct dependency of ExtIO_HackRF.dll) and any dependencies that HackRF.dll has, and then distribute this set of required DLL files in a ZIP file along with your ExtIO_HackRF.dll (instead of doing what you are doing now, which is only distributing your own ExtIO_HackRF.dll file)