Hello Kobold,
Which OS, which Ver. of SAPI installed ?
(Maybe the Wave-Channel in Mixerpannel ??)
The voices can be configured with some parameters.
(But i didn´t reach to configure them via C, yet)
You can configure these parameters via system-configuration-panel.
Theses parameters implement :
Voice (there are different available for download)
Speed (very fast would maybe result in a non-hearable style)
..
I tested under WinXP-Home, too.
It run without problems.
(Was a XP-Standard-Installation no special features selected)
By the way, running Linux i found MBROLA-Project very suitable.
(maybe a hint of cross-plattform-independance)
Tino