It could be the video card, or if might be the backlight on the monitor. With the monitor switched on can you bring up the monitors onscreen menu? If you can see the onscreem controls menu then the monitor is probably okay. If nothing comes up then it's possble the monitor has failed. I've seen as many monitors as video cards fail in my time... so could easily be either issue. If you have multiple inputs on the monitor make sure you have the right one selected. If you have onboard video (not a separate video card) then it could be faulty main memory. The onboard video usually reserves some of the main memory. If you have multiple memory sticks in the machine try swapping them over, or just leave one stick in (usually the one nearest the processor feeds onboard video).