Cannot change desktop background in Windows 7 Home Premium

THANK YOU

I had a virus that turned my desktop background to solid black.  Using autoruns I was able to identify and delete the virus. However, I stll cannot change the desktop background from solid color black.  I right click on the them, but do not have the option to delete.  When I choose a different theme, it appears briefly at the bottom of the window, but when I click off the personalization window, the solid black them replaces my choice. The same is true for screen saver.  I choose bubles, for example.  It is shown at the bottom of the window, but when I click away from the window the screen saver reverts to none.

What if the properties option doesn't exist on the menu when I right click on the desktop? When I go to appearance nothing is there to change and even when I go to the actual picture that I want as my background and right click it and select "Set as Backgrount" I still am stuck with the default picture of that flag. I cannot change it no matter what I try. I am about to throw this computer across the room! Why do they make things so difficult?

thanks i was going crazy  but i read you comnt an vuala tnx