I’m a sucker for good themes to make my Windows XP systems look all pretty. That’s why I have been using the Zune theme. Lifehacker has pointed to a dark blue theme that is very nice that was done for Windows Embedded systems that can be applied to XP (wallpaper not included):
You can download the Embedded theme here.

{"source":"https:\/\/gigaom.com\/2008\/10\/09\/cool-blue-xp-th\/wijax\/49e8740702c6da9341d50357217fb629","varname":"wijax_da744265115827b17e753507c4c736a9","title_element":"header","title_class":"widget-title","title_before":"%3Cheader%20class%3D%22widget-title%22%3E","title_after":"%3C%2Fheader%3E"}