Try the following;
1. Download the latest version of nLite from ;
CODE
www.nliteos.com
Install this version and remove previous versions.
2. Run your original source CD through this version only using an original copy of XP (I recommend XP Pro personally)
3. Keep OEM Preinstall in the unattended section and fill in your other details if you are using an unattended setup.
4. Under the patches section make sure you ENABLE unsigned themes (it is disabled by default).
5. Once nLite has finished then goto the source you are using on your HDD (the folder which contains the I386 folder) and create the following folder structure.
$OEM$\$$\Resources\Themes
6. Into this folder place your theme file and folder.
7. Now open your WINNT.SIF file with notepad and enter the following at the bottom;
CODE
[Shell]
CustomDefaultThemeFile="%WinDir%\Resources\Themes\[enter your theme name here].theme"
This is where you were going slightly wrong there are no spaces around the equals sign (=)
8. Press Ctrl+S to save the edited WINNT.SIF file.
Enjoy!
If you are having problems with your sounds I can help with that too.
Hope this helps

Stoner81.