O assistente Configurar seu microfone está oculto no SpeechUX.dll. Você pode chamar SpeechUX.dll da seguinte forma:
rundll32.exe "%windir%\system32\speech\speechux\SpeechUX.dll", RunWizard Tutorial (Speech Recognition Tutorial)
rundll32.exe "%windir%\system32\speech\speechux\SpeechUX.dll", RunWizard UserTraining (Voice Training)
rundll32.exe "%windir%\system32\speech\speechux\SpeechUX.dll", RunWizard MicTraining (Microphone Training)
rundll32.exe "%windir%\system32\speech\speechux\SpeechUX.dll", RunWizard UserEnrollment (Set Up Speech Recognition)
Então você basicamente quer:
rundll32.exe "%windir%\system32\speech\speechux\SpeechUX.dll", RunWizard MicTraining