Is there a speaker near the screen? That might do it. Otherwise, if it's similar to a desktop monitor, there should be a 'degauss' facility somewhere in the screen settings. On a desktop, this is usually found in the menus accessible with the buttons on the front / side of the monitor. Failing both of those, it could be a graphics card problem, or just the display settings. Try right clicking the desktop and select Properties. You should find a Settings tab, and an Advanced button, which may enable access to your graphics settings. As I said, I'm only guessing all this, from a desktop monitor prospective, so apologies if it's all wrong.