Go ahead and try them without training. The error rate is too high so consider a transcription service. Do not use any that you see here as the spammers lock onto you fast.
I have literally hundreds of hours of excellent quality audio of my (late) father speaking. I would very much like to be able to use Windows 7 voice recognition to transcribe these audio's into text, but from what I know about speech recognition apps - they all seem to require training via a microphone (not an audio recording). My question is whether any of you here have managed to do what I would like to do, either with Windows 7 or any other voice recognition app?