I found 2 problems of your question.First one is,your question isn't complete,you named it speech to text software(but i think you don't need a software infact)..there are lots of software present now which converts speech to text efficiently..you find them easily if you google them.
Secondly,you tag it C++,C#,NET.I want to ask you,are you sure on which platform or language you will use to develop it?I ask you it,because different approaches need if you want to develop it in C# or C++. In C#,Microsoft Speech Api and System.Speech.Recognition dll will done every hard work for you.You will need just few lines of code to implement it.
As i developed a similar speech recognition project in C#,then i will recommend you to see the tutorial over this topics from here..
http://www.prodigyproductionsllc.com/articles/programming/simple-speech-recognition-using-c/[
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I think this is a very good tutorial for a new developer who wants to work with Speech Recognition.Best of luck..:)