Q: my desktop wallpaper has disappeared completely. It has been replaced by a plain blue background. When I shut my computer down, the wallpaper appears briefly before it shuts down. Any thoughts?
A: Usually it should be something to do with a vbirus, if not then i would expect that the OS can't find something it needs, and returns to normal. Maybe, there should be some way of restoring your os (in XP and i think Vista) back to a previous point, probably where something was installed.