When i load pics from my digital camera onto pc they always appear underexposed. why?

Pics viewed on camera screen or via sd card connected to tv seem perfect. loading pics to pc results in underexposed pics. this happens with 3 different digital cameras.
Answer
It seems your monitor for your pc needs to be calibrated since the pictures from 3 different digital cameras appeared to be underexposed on your monitor. there are many software for calibration of monitors to display correct brightness and color. the price range is from 30s to over 300 but i would start with free software for right now.read the following links and ad your monitor.http://www.epaperpress.com/monitorcal/http://www.northlight-images.co.uk/viewing.html