|May I ask if you were uninstalling programs the proper way? By that I mean either from a provided uninstall or via the Control Panel. If you just deleted files then you might have accidentally deleted something you shouldn't.|
If it is a very small dot it might just be a faulty pixel on your monitor. I'm wondering if you have somehow removed the Wallpaper folder or some third party wallpaper program, hence the black screen. What programs did you uninstall?
If the system wallpaper facility is still present then you should be able to get the default wallpaper (at least), via the Control Panel or by right clicking the desktop and selecting Personalize. Maybe it is set to "none".
Please come back and let us know how you got on.