Diferent color in IE on windows

i have a problem…

i made a website for my mothers compagnie… i tested it on my mac with safari, firefox 1.0 and IE and everything is fine., even dreamweaver don’t give errrors. But if u watch it with IE on a windows PC (myself with Windows XP on a Compaq presario R3000) and my mother at the company the background behind the fixed background shows almost white. Does someone knows a solution.? First i thought it was because the BAckground images was transparent but even that wouldn’t work i was told.
the website is

Kind regards DNA