I just bumb to very intresting article at acts of volition about windows XP GUI. I have build Intranet for Windows XP look and feel because we thougth that XP GUI would be good in usability wise. Well it is sort of (comparing to other windows) but those icons and edges are really half done. Also GUI in general is not nice looking, well yes I bet it is very hard to come up with a GUI when audience size is a world.
But still less is more, if I want blue I should have it via themes and default should be plain always.
You can read whole article at acts of volition web-site.
And oh yes, if someone can find me good design guidelines howto make designs on Windows GUI I buy a beer.