look at the back of your pc. if it a pre built it may have a video card installed in it. look to see how many and where the video ports are. if there is an onboard video it going to be where the slot covers are as part of the mb case. if your using a vga monitor and a adapter the adapter may no be working. on new build make sure the 4/8 pin pci power is connected if not there wont be any video.