Black Screen When Running FurMark and Almost All Games

@iCsav:

Just so that we're all clear on the hardware angle of things, do you have the 6 pin power connector plugged into the GPU?

The problem that you're having could be explained by that connector not being plugged in.

So. An update guys.
Some things I noticed recently:

1. The full screen issue (post #3) was solved by itself within a day or two of posting. I has come up again today. Same stuff as earlier. Only difference was that this time, when I pressed some keys, I heard the sound that is played when a key is pressed numerous times in succession or no command is assigned to the key.

2. In the Speccy screenshot I'm posting below, I saw that all of my PCIe slots were being used. I had a look at the motherboard recently, and iirc this was not the case. I'll check again to be sure.

3. In the second MSI Afterburner screenshot, I noticed that the temperature limit was set to 80 °C. Could this be a problem?

4. As I had mentioned before, Osu! was the only game I could play just fine. Today, I found that after testing another game for the same results and then the full screen video one, even osu doesn't last anymore. I can hardly try 1 round and when displaying results or going back to main menu, the BSOD happens. Somehow, now I can't even open GeForce Experience. BSOD as soon as I go to that window.

@Mellon Head: Sorry, I was not keeping track of the thread so I didn't notice your post. I check it as soon as possible.
I'll test for the RAM today, though I can't say about the PSU pin.
Anyways, here are the screenshots. I took as many as possible to capture all relevant information.