It would help to know what OS you're using, but if you have an install disc (you must have since you built this system), I'd try booting from that to see what has happened. Another thing to try is to press F8 about once a second when you power up and see if you can get to the advanced boot menu. If so, try Safe Mode. Usually your mobo will have documentation for how to get into the BIOS too (by pressing a key at power up). When you have more than one video interface, you have to be very careful to make sure they don't interfere with each other as they can easily do. You could try removing all but the onboard video and seeing if that would allow you to boot and get some form of display.
Whenever I turn on my computer the screen is just black I know the computer is on because I hear the start up sound through the speakers. There is no start up screen/bios.
I built my computer a year ago and it has 4 gb of DDR3 and an ATI Radeon 4860 A quad core proccesor (not sure of the specs for it) and 300 gb hard drive My monitor is just a tv with a HDMI chord from it to my computer. Every time a use it to play single player games it is really slow and laggy even on low settings. I wasnt sure if my computer was using the Video Card So I went to Device manager and looked at the Display Adapter and it said I had 3 video cards running ( the Raedeon 4860 Video card, Radeon 3360 or something like that, and another video card.) So this is when the problem arose I clicked disable on the Radeon 3360 and the screen went blank.
So I restarted the system but the screen was still blank. I Tried using a VGA cable instead of an HDMI and it still wouldnt work. I tried removing the CMOS battery for a while and it still wouldnt display anything on the screen. I tried using a normal Computer monitor with a VGA and it still didint work. I tried to do a system restore blindly by pressing the windows button and using my other computer to mirror the system restore but I could here the error sound through my speakers So something wouldnt let it restore.
I have looked up how to reset the Hard drive or reset the computer to factory settings and most ways involed using the BIOS which I cant see or use. Anyone know a way of fixing the black screen problem or a way of resetting the computer without having to use BIOS or windows? Any help is apreciated. Thanks