This is an issue with the windows System.Speech library itself. For whatever reason only a limited subset of installed voices are listed. I have no idea what makes the difference between one that is and one that isn't.for sh#ts and giggles I downloaded some more of the official MS Windows voice packs... and now Explorer lists Microsoft Hazel and Microsoft Haruka (though she speaks Japanese which I cannot understand, she sounds awesome!) LOL
Weirdly some of the other voices do not get listed in Explorer. hmm