The Tablet PC Experience pack (or whatever it was called) came with a rather nice theme that originated on Media Centre, finally its available on XP:
New Windows XP Theme (Energy Blue) Available.... ..., you can now download the Royale / Energy Blue theme. This theme originally shipped with Windows XP Media Center Edition, but Microsoft New Zealand have now released it in a form that can be installed on Windows XP Professional and (I assume) Windows XP Home Edition. It's the best dressed you've seen Windows XP ...
[via Tim Sneath]