Option to change wallpaper is missing or unavailable

Want to change your desktop wallpaper, but finding that the option to do so in the Display Properties dialog box on your XP computer is not there, or grayed out? This can happen if a registry key is set to hide or lock the display settings. Did you say you never changed such a setting and nobody else uses your computer? Well, it can be done by malware, too. To find out how to fix the problem, see KB article 921049