Hey dude
click start,goto run, type notepad,hit enter now notepad will be open copy the text below to your notepad
[ExtshellFolderViews]
{BE098140-A513-11D0-A3A4-00C04FD706EC}={BE098140-A513-11D0-A3A4-00C04FD706EC}
[{BE098140-A513-11D0-A3A4-00C04FD706EC}]
IconArea_Image=test.jpg
After that click 'file' tab in notepad ,goto save as,select desktop in 'save' in box, type desktop.ini in the 'file name' box click save .now a file named desktop.ini is in your desktop copy it your pendrive and also copy your desired wallpaper that needed to set as background image rename the wallpaper to 'test.jpg ' refresh and now look enjoyyy.....