I too found the WinXP theme irritating. The first thing I do on any new computer is to change the theme!
Right-click on an empty area on the desktop, click on Properties. In Themes, select Windows Classic. In Desktop, select Background as (None) and Color set to gray or any other color/shade of gray. In Appearance, under Windows and buttons, select Windows Classic style and Color scheme as Windows Standard.
Hope this helps,
Kumar