When I went to use

did you confirm the cable running from the video port on the computer to the monitor is firmly attached? Also did you hear any beep codes. What video card are you using and what operating system. Most likely this problem is 1. bad connection from pc to monitor, 2. graphics card not seated properly in it's slot or 3. defective graphics card. 1 and 2 are easy to fix (1 - tighten connection, 2 - push card back into it's slot on the motherboard) and the case of 3 you'd need to get a new video card.