There is a theme made by windows that came out with XP Tablet Edition, but is compatible with Windows XP! It is very similar to the normal XP theme but I think it looks loads better.
If you want to use it you have to manually install it because the installer will only install it on XP Tablet Edition.
First off download the installer from Microsoft.
Use Winrar to extract the exe and manually place the following files in the following location.
C:\WINDOWS\Resources\Themes\royale.theme
C:\WINDOWS\Resources\Themes\royale\royale (its the Windows Visual Style File)
C:\WINDOWS\Resources\Themes\royale\shellstyle.dll
C:\WINDOWS\Resources\Themes\royale\wallpaper\energybliss.jpg
Bin the other files, they are not needed.
Right click in the desktop, click properties and the new theme will appear in the "Themes" tab!!!