I tried to associate STEP files to Rhino5x64 but only 32bit Rhino will work.
When I use Window’s “Open with…” dialog and browse for the desired program, it doesn’t accept Rhino.exe in the Programs folder, only the Rhino4.exe in the Program Files (x86) folder…
Windows 7 Enterprise SP1 here as well.
I can select the Rhino.exe in the C:\Program Files\Rhinoceros 5 (64-bit)\System directory. And it will open in 64-bit.
The only thing that is strange is that the Open with box says Rhino WIP after having selected the exe.