Watching Netflix, loud buzzing noise and black screen.

Hey all. I have this problem I cannot figure out. When we are watching Netflix, sometimes, about an hour in, my computer will go black, freeze up and make a loud buzzing noise through my soundbar. The only thing to do to get out of it is a forced restart. Any ideas what it would be? This is a HTPC I built a year ago and just recently put a 750ti GPU in it to play iRacing. It probably has been 3 months since the install of the GPU, but I never have it happen when I am playing that game. I also just checked my BIOS for voltage levels and they all seem good as well as running a good memory test.

Thanks for any help!