Have older machine dell which has a VGA divi graphics card. It has Windows XP. Computer was working fine and then it was moved. We cannot get the VGA display to work. I have tested both monitor and cable. It works. I reseated graphics card. There is no other VGA port Since nothing appears on screen-no signal. I do not know if there is driver, card problem or slot problem. I cannot troubleshoot very well since there is no screen. Any suggestions?