OK, OK, Windows is not the most popular thing on a site like this. Still, there are some Linux users who want their desktop to look like Windows XP's "Luna" theme, whether it be for pleasing a new and shy Linux convert, or just because they enjoy the irony.
This is a theme for the Gnome panel (or KDE Kicker) that complements any other Luna-like theme elements. The patterns are created by myself using GIMP. The "Luna-blue" version was created first, and then a selection of other colors.
Also recommended for Windoze fanboys...
Lunacity theme for Metacity: http://www.gnome-look.org/content/show.php/Lunacity?content=62350
Lunacy GTK Theme
GnomeXP Icon Theme