monitor turns off but pc stays on. Not sure whats happening

[bigboi972]

2 weeks ago I started having an issue with my pc. When I boot it up and I open programs my pc monitor goes black. Now I know its not the display because even if I am playing music and it goes black all sounds stops letting me know that its not just the display its something greater. I sent my motherboard off to the manufacture and they sent me another one back. I also reformatted the hard drive and I am still having this issue. I have also deleted current drivers and installed older ones that are 3 months old and even 2 years old to try and fix the problem. I am really desperate here and I am not sure whats going on. I hope someone can help me I have linked a video below ignore everything in the video that I say the only part that applies is the part where the computer turns off when I open programs

https://www.youtube.com/watch?v=3Tdj3SmV-eM

 

[jsquareg]

I had the same problem a few weeks ago. I found it was due to my APC battery backup. For some reason the threshhold level for the thing got out of whack. I reset it and that took care of the problem.