This is all due to different screen resolutions. Your Notebook computer may be set to a resolution of 800 by 600 pixels while the classroom computers are set to 640 by 480 pixels, or vice versa. When you create a picture on a resolution of 800 by 600 pixels, only part of it will appear on a 640 by 480 screen. Contrariwise, a 640 by 480 picture will look small on an 800 by 600 resolution, and will leave part of the screen unused. To solve the problem, simply decide on your favourite resolution, and set both the Notebook and the classroom computers to it.