We will take a closer look at changing, downloading, and creating backgrounds in Chapter 11, "Creating a Background Library." However, let's examine what happens when you change the background for the current theme (using the Luna theme as an example).
To change the background, select the Desktop tab of the Display Properties dialog box (right-click the desktop and select Properties to open the dialog box). Select any of the backgrounds found in the Background list box. When you select a new background, you are actually modifying the current theme.
For example, let's say you are currently using the Windows XP theme (Luna) and you select a new background on the Desktop tab. When you switch to the Themes tab of the Display Properties dialog box, the current theme is now named Windows XP (Modified), as shown in Figure 3.11.
Figure 3.11. Change any element of a theme, and you are in essence creating a new theme.
By changing the background, you have started the process of creating a new theme, and you can save this new theme under a new name (using the Save As command on the Theme tab). We discuss this process in detail in the next chapter.