Windows XP default theme missing!
Sometimes the default theme of Windows XP will be missing from the Themes tab in Desktop Properties, and there will be only Classic them in the drop down list. This is one of the common problems I have seen ;-).
To recover the default XP theme (also called as Luna theme), the following solutions can be used:-
1 Start the Themes Service: Go to Start > Run and type services.msc and press Enter key to open the Services window. Here, navigate to Themes service, and right-click on it and select Properties, and make sure that the Start Up type is set to Automatic. And if the service is stopped, click the Start button to start it.
2 Locate the Luna.theme file manually: Right click on the desktop and choose Properties. On the Themes tab, choose the Browse... option. Next browse and locate the file C:\Windows\Resources\Themes\Luna.theme and apply this as theme.
3 Luna.theme file not present: If Luna.theme file itself is not present, then it has to be restored back. Download this Zip file from Kelly’s Korner, and then extract the contents of this file to C:\Windows directory. Then, apply this theme as given in previous step.
4 Registry fix: If the above steps do not solve the problem, then there is a chance of changes in the default Registry values related to Themes. Download this Registry fix from Kelly’s Korner, and merge it with the Registry. Restart the computer to make the changes to take effect.