black screen startup

not sure what was done to the machine previously. When I turn the machine on everything sounds fine the hard drive is spinning but I am not getting a signal to the monitor. I am thinking it may be the video card or mother board. I took out all other cards and tried unplugged cd rom. still nothing. When I put a startup disk in, I get the same black screen and the 3 1/2 isnt lighting up but I am not sure if the bios is set to boot to 3 1/2 first. The monitor is fine. The numlock or cap lock on the keyboard will not respond either. Any suggestions on what to do next.