Can't change wallpaper

After removing a virus (Spyware Doctor and Norton) downloaded, I can't change my wallpaper.  I right-click,  go to properties, then desktop, and the box is shaded, as in inactive.  The little picture of the monitor shows a blue screen - the same blue that was there when the virus was active.  Everything else works fine, but I can't change my wallpaper.  Any ideas?  I tried system restore and refresh driver, it didn't work.  I also tried to change the settings on HKEY_CURRENT_USER\ etc that Microsoft reccomended, no good.  Also tried gpedit solution, didn't do it (the jpeg shows on the list, but wallpaper choice "box" is still shaded).  Thanks for the help.
 
ASlater
 
My specs:
 
   Operating System             Microsoft Windows XP Professional 
     OS Service Pack             Service Pack 2
     DirectX                           4.09.00.0904 (DirectX 9.0c)
     CPU Type                       Intel Pentium 4, 3200 MHz (16 x 200)
     Motherboard Name          Dell Dimension XPS Gen 2
     Motherboard Chipset        Intel Canterwood i875P/E7210
     System Memory              1024 MB  (PC3200 DDR SDRAM)
     BIOS Type                      Phoenix (02/19/04)
     Video Adapter                 256MB DDR ATI Radeon 9800 XT Sec 
     Video Adapter                 256MB DDR ATI Radeon 9800 XT 
     3D Accelerator                ATI Radeon 9800 XT (R360)
     Monitor                           Dell 1901FP (Analog)  [19" LCD]