can't able to change my windows desktop

hi friends..
yesterday when iam browsing my desktop wall paper suddenly changes to the wall paper named "jobs rapido"...After that i try to change the wall paper but it can't change...
plz anybody solve my problem??

Thank u in advance..

what happens when your try to change the background screen from the look and feel properties ?

when i change wallpaper, it doesn't change any thing..simply it display as it is..

1-Right click on a empty space on the desktop and click on Personalize.
2-Click on the Desktop Background link at the bottom of the window.
3-Click on the drop down arrow menu to select from the list of available picture folder locations, or click on the Browse button to navigate to the picture folder location.
4-Right click on an available picture, or click (check) on the box in the upper left corner of the picture, to select it.
5-Click on the drop down arrow menu, and click on the picture position you want for the desktop background.
6-Click on OK to apply the changes.
7- Close the Personalize window when done

Is it Windows 7 editon?
You can check out this blog for details sayng that it comes to can't be changed or customized.
http://windows.microsoft.com/en-US/windows7/Personalize-your-computer

No...windows XP...
But now my problem was done