no signal on newly built computer

i built a computer. i started it up connected to a monitor from another computer, but there was no signal. the video card is in the motherboard. i tried a different video card. the power is 20+4 pin. there is a 4-pin slot on the mobo that i plugged the other 4-pin connector to. the monitor works on the other computer. when the monitor is disconnected it says "please check monitor cable. when i start it up, the fans run at full. sometimes when i shut it down, the power supply fan still runs.

Sorry to be so late in responding to your post. Please provide a complete list of all the components that make up your build, and, the cat # of each of the components, and a confirming statement that all components were purchased new. For the monitor you are trying to use, provide the manufacturers model # and part # from the mfgs label on the monitor.