Windows does have this built in. It's called Windows Voice Recognition.
You have the spend about 20mins training it, but it works rather well.
If you're using XP I don't know where to find it, but in VISTA and Windows 7 it's under Control Panel> Hardware & Sound> Sound > Recording Tab> Right Click Microphone > Left click configure Speech Recognition
I'm not sure anyone can help you with that.Made my day it works well but it tires my voice, not used to speaking that much.