Howdy -
It's been a while Since I tried to get the Houdini engine into Unity. First time on this current machine.
After I load my Houdini engine package into Unity, I check the installation and I get this:

DllNotFoundException: libHARC32
HoudiniHost.getEnvInt (HAPI_EnvIntType int_type) (at Assets/Houdini/Scripts/HoudiniHostWrappers.cs:56)
HoudiniHost.initialize () (at Assets/Houdini/Scripts/HoudiniHostLinker.cs:91)
HoudiniHost.initializeHost () (at Assets/Houdini/Scripts/HoudiniHost.cs:278)
HoudiniHost.isInstallationOk () (at Assets/Houdini/Scripts/HoudiniHostLinker.cs:43)
HoudiniHost.displayHoudiniEngineInstallInfo () (at Assets/Houdini/Scripts/HoudiniHostLinker.cs:171)
HoudiniMenu.about () (at Assets/Houdini/Editor/HoudiniMenu.cs:115)

A few years back I had a similar problem with the old HAPI library. I updated my PATH such that the Houdini installation was the first item. However, this did not resolve the problem.

I am working with Unity 5.0.0b9(64 Bit)
Houdini houdini-15.0.244.16-win64-vc11
Running windows 10 on a 64 bit machine.

Any Suggestions?

Please update to the latest Unity 5 and latest Houdini 15. Both of those versions are very old now. The Unity you have is still the beta.

Before you do update, I recommend you uninstall all your current Houdini installations and Unity so you can start with a clean slate.

Finally, you should remove any mentions of Houdini from your PATH. It's no longer required and can actually harm your installation if you have the wrong paths in there. The Houdini Engine plugin should find the correct installation of Houdini automatically.

Thank you very much for your suggestion Damian.
I updated to the newest version of Houdini and the newest version of Unity and it worked very nicely, just as expected.

Thanks for the warning about the PATH Variable. That could create havoc if not watched after.

Cheers!