On many modern laptops the mouse touchpad is capable of zooming in and out by using two fingers on the pad at once. pulling two points away from each other makes it larger and "pinching" it reduces the size. It's similar to an itouch or iphone's ability to enlarge the screen for easier readability. Sometimes on my Dell XPS my arms my rub against the touch pad and change the font of the screen. try putting two fingers on the mouse. keep one still and drag the other away from and closer to the still finger to see the results. good luck.