Color Pallette Not Working

I can view all of the colors in the color pallette, however, when I select a color (typically the brighter color -- magenta / pink / neon green, etc) they appear toned down and duller in the actual image. I can see them how I want them in the color picker / swatches, however, I can't get those colors to work in the actual image.

Is there a setting I am missing?

Please help.

Adobe Photoshop CS3 w/ Windows Vista
Lenovo x60s - 2G Ram, 100 gb HD. LCD Screen

What colour mode are you working in?

My guess is you're running int the limitations fo the CMYK gammut