My HP W19b LCD monitor has large areas of the

LCD screens are a little more complicated than that. You can try taking apart the outside (the screen is inside of the plastic, it's not hard there are just screws all around it) and making sure all the connections are good, this has definitely worked for me in the past but other than that the cheapest solution is to buy a new screen, LCD's require specialized equipment to re-polarize the layers if the screen itself is dissambled.

Could be the monitor or could be the video card in your computer. Try another monitor or try this monitor on another computer to determine which. Either way, it's not a repair you should attempt. Modern electronics are all circuit boards and miniature components and not something you can "solder". Get another monitor or have the video card replaced.