Using a Radeon 5450 with HDMI and DVI, 1 or the other. Same problem with each. I turn on the computer and the monitor stays black. Most times it turns on. It seems to turn on more often when its been off all night. (I unplug the AC cord from the wall at night for other reasons.) Sometimes it helps if I remove the battery and activate the power switch to discharge the capacitors. I don't have another graphic card to test. But when its on and the monitor is dark I can access its hard drive on the network so its obviously on.