http://www.techili.com/desktops/091105-download-free-windows-xp-and-windows-vista-themes-with-mycolors.html

This is the best source to download Free Windows XP and Windows Vista Themes. They are in a great variety of categories, topics, colors, moods. You can choice what resolution fits you better and best of it is that you can get all these themes for free. Just Download them and start using one for each...