Most laptops do have a Scroll Lock button, its just hidden away as an FN Key combination. You probably have a function key, generally between alt and ctrl. Look for a an icon on your keys, a small square with an arrow pointing down towards a line. Might be PGDN like on my keyboard. You just need to hold the FN Key, then hold the appropriate key for Scroll Lock, then hit PrntScrn, and you've taken a Screenshot.