display problem for compaq notebook 3000 series

Hi, there,

I just bought a Compaq 3077WM notebook. It has a SXGA 16" screen.
However, when I display an image with smooth transition from brigth
blue to dark blue, it appears not smooth. Also if we display other
images with high variance, there seems some block there (the
transition is not smooth).

For some old PC, this phenomenon happens when we choose 16bit display
to display some images with high variance. However, in my current
Compaq system, I've chosen 32bit display. Then what's the problem
here? Is it a problem of display or video adapter?

Thanks,