Computer keeps restarting itself with no known prompt

I've had this computer for 3 and a half years now, and only a week after I got it, this problem started happening. At first, I thought it was just malware, and after running my antivirus program and getting things cleaned up, it happened less frequently and I thought I had solved the problem. But as my 1 year warranty began to run out, I decided to confront Dell with the issue and see if they could help me fix it.

The problem goes like this:

I'll start up my computer (after having shut it down correctly using the start menu) and everything will run fine. I'll log on, my startup programs will open, and I'll begin doing whatever it is I needed to do. Then, out of nowhere, my computer will restart itself. I won't know when it'll happen, I won't know why, there will be no window that pops up saying that my computer needs to restart for a Windows update or anything. I'll just be working on something in Photoshop or browsing the Internet and suddenly, black screen, computer shutting down, computer starting back up, Dell startup screen and then the message prompt you get from holding down the power button while the computer is on (a hard shut down) that says "Your computer was not shut down properly. You can boot with Safe Mode, Safe Mode with Networking, or Start Windows Normally." I don't exactly know what it says from memory because there's a timer that counts down for me to make my choice, but I always start back up normally.

Now, sometimes my computer will start up normally with nothing wrong, and then repeat this same restart process again, or it'll be nice and not do this for the rest of the day. Sometimes it'll stay up for another 10 minutes before deciding it wants to restart again. I have no idea when it'll happen, and so it's frustrating.

When I contacted Dell to get this fixed, we ran through every possible test you could do. I did a regular system restore, I left my computer on overnight to have them monitor it, I reinstalled hard drives, I had the motherboard replaced, I had the power cord replaced and I even went so far as having a complete factory reset done on it. That last part seemed really cheap, though, because I lost the Microsoft Office I paid extra for when ordering the computer, and not only a week after did my computer start doing the resetting business again. So not only have I lost money, but I still have a faulty machine even after asking several times if I could just have it replaced with a new one, just to be rejected.

So, my question is: Is there any fix for this? What exactly is wrong with my computer? I have run through every possible problem, but nothing adds up, and with a factory reset it shouldn't still be doing this. If anyone has any answers, even the answer of "You may just need to get a new computer" I'll gladly take it. I just need to know what's causing this.

Here are some screenshots of my computer's specs, and what programs run at startup, if that's any help at all.

For the record, the processes listed here, aside from Chrome as that's what I'm using, are programs I haven't touched since one of these infamous computer resets. I just booted up my computer after the restart, opened Chrome, and wrote this post.