Though being a relatively old article (February 2006), I thought this MSDN New Zealand newsletter article was worth mentioning. While Googling to see if there was a way to use XP’s text-to-speech capabilities using the .NET Framework, I stumbled across this article that talked about the System.Speech namespace that will debut in .NET Framework 3.0 (a.k.a. WinFX):

System.Speech… allows developers to easily speech-enable Windows Forms applications and apps based on WinFX in both Vista and Windows XP. In addition, there’s an updated COM Speech API (SAPI 5.3) to give native code access to the enhanced speech capabilities of the platform.

Speech technology encompasses two technologies: synthesizers and recognizers. A speech synthesizer takes text as input and produces an audio stream as output. Speech synthesis is also referred to as text-to-speech (TTS). A speech recognizer, on the other hand, does the opposite. It takes an audio stream as input, and turns it into a text transcription.