When you have problems with your video display, it can be something as simple as having the brightness turned down to low, to a bad controller on the video card. If you have not done this first learn to identify the components of the video display system. When you look inside any open computer, see if you can locate the Video Card.
Is your video card mounted in an adapter slot or is it integrated onto the motherboard. If the card is motherboard integrated, locate the jumpers that will allow the card to be disabled should you need to install another card.
The Monitor is the second component in the video display and it must be compatible with your video card. Be sure the maximum resolution of your video card and monitor are the same. Its even better to your a higher resolution display on your monitor.