Shoutbox

Just recently my sister's computer has been having problems. There are two profiles, hers and the visitor profile. When she logs into her profile, the whole screen is black, only showing icons on the taskbar and on her desktop. Right clicking doesn't work as it is hidden by the "black", and as well the task manager doesn't show (only the icon on the top left of the box). The visitor profile works just fine. I'm running a virus scan for her now, but other than that is there any ideas as to what the problem is?

Thank you, help is much appreciated.