I was working the helpdesk at my college a few years ago and was watching some of the users coming in. One girl was leaning forward and looking up the screen, then asked for help. When I got to her, she said she was having difficulty seeing under one window to read the Word window behind it. I showed her how to switch windows by clicking the mouse. I found out later, that the year before, this same girl had aced the Windows course I'd seen her in and was currently taking an advanced course in it.