troubleshooting

i have ibm pc aptiva working on the problem is this i am not getting anything form the monitor but power. no picture, but the cpu boots up its an (300gl personal computer) i have done a little troubleshooting using a video card instead of the onboard video that it has but its still the same i am going to remove each card that is on the board piece by piece and startup without each to see if any of those i not working, have anyone else had this kind of problem before an can help me it will be greatly appreciated,, awaiting your response