Since I posted yesterday, I've gotten some questions about the TTS engines that Microsoft includes in the OS itself. Well, here's the deal...
Microsoft has shipped TTS engines in the OS before. In the Windows XP time frame, for example, we shipped three different voices that were all based on the same underlying technology: Microsoft Mary, Microsoft Mike, and Microsoft Sam.They were OK, but certainly not something you'd want to listen to all day long (IMO). You can hear what they sound like here: Microsoft Mary, Microsoft Mike, Microsoft Sam.
In Windows Vista, though, we've completely revamped the technology. As a result we have a "new" voice built right into the OS named Microsoft Anna. Here's what she sounds like: Microsoft Anna.
As you can tell, Anna sounds more human than Mary, Mike, and Sam. As time goes by, the voices will become more and more natural. Someday, you won't even be able to tell the difference between a synthesized voice and a real human voice.
By the way ... I created these .WAV files by simply using one of the sample applications included with the SAPI 5.1 SDK, called TTSApp.