September 23rd 2010.
Windows 7 and Windows Vista come with Speech Recognition built in.
To set it up, go to Control Panel / Speech Recognition
First set up your microphone for correct use (It is best to use a headset microphone). Then run the interactive Speech Tutorial, which teaches you many of the commands, and also learns your voice as you speak. Then Train your computer to understand you . Passages of text are displayed on the screen, and all you do is read them out loud into the microphone.
Take a look at the Speech Reference Sheet. It is also worth visiting
To get a handy list of commands which is easier to print.
Windows Speech Recognition in Vista and Win 7 is available in eight languages/dialects: English, French, Spanish, German, Japanese, Simplified Chinese, and Traditional Chinese. These other languages can be added to the Ultimate Editions of Vista and Win 7.