Win 10 all okay BUT! Librarian won't install

[docdelete]

I've had my SH-201 working with Windows 10 for some time - using the Test Mode bypass to get the Win8 driver to work. But, here's a weird one for you - I have the Editor software installed and, for some reason, opted not to install the Librarian on this current PC. I'm trying to install it now and the installer fails! The error indicates that the installer can't find it's own MSI file!! (Like what would happen if I deleted the package files half-way through the process, but clearly I haven't.)

This installer worked fine in W10 2 years ago, and at all times prior to that. Screenshot attached.

Does anyone have any brainwaves? Or, can someone point me at the Librarian EXE file so I can see if a dumb 'portable' install will work?

Thanks all.