no walllpaper or background option

I've lost the ability to change the wallpaper on my computer. when i go to "display properties" i have tabs for 'themes', "screensaver', 'appearance' and 'settings' but nothing for background. and there are no options on the themes tab. the background tab just seemed to disappear. i'm running windows XP and have had a look at tweakui and group policy editor but can find nothing that indicates backgrounds have been disabled. any thoughts on how to fix this??

 

Hey thanks for the info...

I also found that using the group policies, it could be remedied by making sure the "classic shell" option is disabled.