I am one of the (many) persons that didn't like Luna, the default Windows XP style/theme. The first thing I usually do when running a new Windows XP installation is to change the theme to Windows Classic. It seems to use less space, and the colours are not that "bright".
I have seem in quite a few blogs around the Internet references to the Windows Media Center theme, and Microsoft New Zealand made it available as an individual download. The Royale theme is better looking than Luna, with nicer colours, similar to the one used on Windows Media Center 2005.
I am using it now on my desktop, tablet PC and laptop in the office. Good for a change.