If you have upgraded form Windows Vista 64-bit edition to Windows 7 64-bit Home edition, then you may have the problem to change Desktop background. Here in this article we’ll try to solve this problem.
FIX : Unable To Change Desktop Background In Windows 7
1. Press 
+ R and put regedit in Run dialog box to open Registry Editor (if you’re not familiar with Registry Editor, then click here). Click OK.
2. Navigate here:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\ActiveDesktop
3. In the right pane of this location, create a DWORD value NoChangingWallPaper and set its Value data to 0.
Now reboot and find whether it works or not. If not continue reading. You can try another registry tweak and you will solve this problem. Copy the below shown text into Notepad and save it as a registry script. In the Save As dialog provide .reg extension to file name and select file type as All files.
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System]
“Wallpaper”=-
“WallpaperStyle”=-[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]
“Wallpaper”=-
“WallpaperStyle”=-
Now in desktop mode right click this .reg file click on Merge. Click on the Run button for Security Warning pop-up. Click on Continue (UAC), Yes, and then OK when prompted. When done, you can delete the .reg file.
Restart PC, your problem should be fixed now.
That’s it!
