I found out also that the sound card in your computer can make a difference.

I had a good one for voice recognition but it made a weird feedback noises when playing movies, videos. So I tried a different one {cheaper brand} and my Via Voice {IBM speech recog software} didn't work very well at all with that card.

Since I got the new motherboard with built in sound I haven't installed the Via Voice yet to test it.

1- High quality microphone {plantronics brand is good}
2- A good quality sound card
3- look thru the settings, preferences or options of your speech recog program and look for sensitivity settings and do the training in a normal speaking voice
4- have a good amount of RAM -512 or more - so system doesn't bog down when other programs are open.