There should be some buttons,or a panel of them on the front/bottom of your monitor. It lets you make adjustments for contrast/brightness/vertical size/horizontal size-position etc. .

One of those settings should let you set it back to defaults i.e. "recall" or some such. It also should have a function for "Degause"(de-magnetize).Monitors usually do this automatically on start-up,but that feature will let you do it manually. Might give it a' shot...