It was not a different shade. It probably was at a different angle. I tried tripod and it was not working (lots of wavy lines) so I upped the ISO and shot by hand. I chose the same desktop color in both windows xp and vista. This color clearly shows the graininess in XP. I went into display properties > desktop and choose "none". Then clicked on "color" and then "other". The color I chose in both XP and Vista was the darkest green (5th row, 4th color from left).
I just found a few colors in Vista that that have the graininess anyway so there goes that theory

For some reason there are a lot more colors in XP where the graininess is apparent than in Vista. In Vista it is pretty much only the medium grays (and one blue/gray).
jaad75,
Do you still have the problem? Earlier in the thread you said that after a clean install fixed the problem. Are you still without problem?