Can't change background

My desktop has a taskbar and all icons as it should but my background is a blue screen. I did a search which suggested going into properties to highlight an address on the web tab from the customize desktop button and delete, then do restart and change the background but that doesn't work. There's no address to highligt. During logging off process, the desktop displays the .jpg pic used as a background with no taskbar or icons and then logs off. Log back on and you get the a blue background. *********THIS IS NOT THE BLUE ERROR SCREEN************

Does anyone know a fix for this? FYI...the pc did have a virus which attacked the desktop and has been fixed with anti-virus software. I don't know the name of the virus but the pc is virus free. Dell Dimension 2300 2.1Ghz 512MB DDR WindowsXP Home Edition SP2