Having monitor trouble need help

[datrell]

Ok the other day I was trying to get my computers networked together and I came to the conclusion I need to get a network card. So I put everything back in the CPU but my monitor doesnt work. I tried that same monitor on another computer in the house and it works there so I know its not the monitor that messing up. Its gets power and everything (green light shows its on) but there's no picture and it says video error so I am guessing when I put everything back together I mustve put something in the wrong spot or unplugged something that shouldnt have been. Does anyone know a site that shows how the insides should be set up to get the monitor to stop showing the video error or can someone help. All help is appreciated