Computer boots but monitor won't turn on?

My husband tried adding a video card to his desktop (Gateway E2500). When we plugged everything back up and turned on the computer, there was smoke coming from the top of the motherboard. We can see visible damage about two inches long and no wider than dental floss. The computer still boots up after we removed the graphics card, however the monitor will not show a picture. We plugged it up to our other computer and it works fine. On the computer that was smoking, the monitor light is on (orange), but never come completely on (green). Any suggestions?