To verify if any are installed then just use the NCH Swift Sound application of your choice and select the Text to Speech option. It will list the names of the available voices.
If you do not have any please check www.nch.com.au/speech/index.html. It includes downloads for the free Microsoft Speech engines.
For reliability of recognition you must train your speech recognition engine extensively. Please refer to its documentation for more details.
Otherwise you must configure the NCH Application to select the engine and the user. The user represents the person who made the original dictation/audio file, not the person who is using the machine. This especially important for Express Scribe where you receive dictations from a variety of sources.