Windows XP Customizing / Cleaning

UXtheme patcher (free)
http://www.windowsxlive.net/?p=604

Themes
Flyakite OSX (free)
http://osx.portraitofakite.com/

Zune Theme (free)
http://go.microsoft.com/zune

TweakUI (free)
http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx

Autostart
...

CCleaner (free)
http://www.ccleaner.com/