Question for photography enthusiasts

[Dr. Flyview]

I'm playing around with my Nikon D40. I've been shooting in RAW. The problem I'm having is that the raw pictures (before any editing) look different in [Photoshop CS4 - Camera Raw] than they do in [Windows 7 preview] / [FastPictureViewer]. The ones in fastpictureviewer look better from the start. What kind of codec is Photoshop using and do I need to get a plugin or calibration file or something particularly for my camera for Adobe Camera Raw??