Unable to imports the System.Speech namespace.

Hi Dude,
i have tried to develope the Speech recognition applications. i have downloaded the few sample from net and try to run the applications in my local computer. Its not work it out. all they were using the "Imports System.Speech"namespace. but in my computer does not have this namespace. so that, the error ir shown, i think. i am using VS 2005. Is it possible to develop the speech recognition in this version? If yes, how should i imports the Speech namespace in my applications. please help me to learn this section. please let me know as soon as possible.
Thank you.