The following links to voices producers have been provided for informational and educational purposes...
Under Windows XP:
Download SpeechSDK51MSM.exe file, unzip files and run setup.exe - and enjoy using new voices Mike and Mary. Do not use Sample TTS Voice it is something else
Microsoft voices are free, but under Windows 7, a high license level is required (higher than Home or Starter)
Commercial producers offer a variety of speech voices in many languages. The voices are in high quality. Functional voices might be tested during the trial period.
Both IVONA and NUANCE voices can be downloaded for example from here: Visionaid
High quality trial voices are also offered by Kobaspeech it is already the third generation of voices. Click on the following links to download the two latest generation of speech voices:Kobaspeech3
Espeek sounds a bit like a robot, but it is free, portable due to small size,
works correctly under most common operating systems such us:
Windows XP, Win 7 etc, Android, Linux, OSX
Espeek speaks English also it is tested and developed under 29 other
languages about half of them should already be usable
Click on the following link to download the Cepstral high quality demo voices. Unfortunatly, there are only a few different from English languages