The TextToSpeechStartup call attempts to find the entry for the DECtalk Software user pronunciation dictionary in the registry at:

REGISTRY KEY:

HKEY_LOCAL_MACHINE
\Software\DigitalEquipmentCorporation\DECtalk\4.30

Value: UserDict

and is set to value:

[user selected dir]\user.dic

If the UserDict entry cannot be found, then the TextToSpeechStartup call defaults to looking in the application’s default directory for USER.DIC to be loaded as the user pronunciation dictionary.

If the user pronunciation dictionary fails to be loaded, then the TextToSpeechStartup call returns a value of MMSYSERR_ERROR.