I have found on most computers you need to go into the mic settings as one of the other posters pointed out and you need to turn the mic volume up high like 80-100% then you need to turn up the db boost to like 75% to get a good sound. If you sound to lound and staticy then back those down a click.
i like to use sound recorder to check how well the mic is working. After you mess with you mic settings. Go to start orb programs accessories and sound recorder.