Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\Administrator>echo %windir%
C:\WINDOWS

C:\Documents and Settings\Administrator>echo %windir%\Fonts
C:\WINDOWS\Fonts

C:\Documents and Settings\Administrator>echo %windir%Fonts
C:\WINDOWSFonts

Looks like you need the slash

cool, just got confused, Greenmachines theme creation guide didnt have one, and i thought it was a type, that he missed out the \, but in the official ms theme files its the same too.

luna.theme

[Control Panel\Desktop]
Wallpaper=%WinDir%web\wallpaper\Bliss.bmp
Wallpaper.MUI=@themeui.dll,-2036
TileWallpaper=0
WallpaperStyle=2
Pattern=
ScreenSaveActive=1

so sorry for thinking wrong.