Windows currently has two speech APIs. One is SAPI4 on Windows 2000. The other is SAPI5 since Windows XP.
However, it is possible to use SAPI5 on windows 2000 or even windows 9x. You can install Speech SDK 5.1 which has included SAPI and some free TTS voices as well as speech recognition engines.
Our TTS products, Active TTS/Speak Aloud support both SAPI4 and SAPI5 voices. It also means they depend on SAPI4 or SAPI5. So the machines should have SAPI4/SAPI5 and some TTS voices installed beforehand.