PCVOZ is one of the best, if not the best, voice synthesizers. It uses a powerful TTS3000 text to voice motor from Lernout & Hauspie, that comes included as a default in the application.
You can configure the voice tone (deeper, higher), type of voice, speed of reading or volume. PCVOZ as a default reads any text that appears on the screen of your PC in a high voice, including the smallest, like window titles etc. Logically the user can configure the synthesizer to only read the texts they wish. In summary, PCVOZ is a highly recommended option for those looking for this type of program.