Hi Nomad;
 
Ahhh.  Now I see your problem; it's a self-built machine!!!  There are 2 things that are common mistakes in self-built or custom-built rigs that people on this forum and the other tech forums I volunteer on cause your kind of problems; both easy to fix:
 
1.  Failed hard drive; re-read my 
Post #2 above!  Test and replace if test fails.  simple.
 
2.  Underpowered or failing PSU. 
 WE'LL NEED YOUR EXACT SPECS ON BOTH THE PSU AND YOUR DISCRETE GPU VIDEO CARD TO FIX THIS!!  We need the Make/Model, Wattage, and Amperage of both the +12V & +5V rails.  To do this, you'll probably have to open your case and disconnect the PSU, take it out and look at it, unless you have those specs on hand.  You won't be able to get this from 
SPECCY either unfortunately; but you should still continue running
 SPECCY for us, as it will give us to poop on your GPU card specs.
 
It's almost 1 or both of these 2 problems with self-built machines that have your symptom issues.  Now we are solving probably 80%-90% of these kinds of failures once we figure out it's a self-built PC.  Here's your problem--and please don't take offense to this.  People who build their own PCs; especially us tekky or IT guys are very remiss to admit they had a design problem or a failed device (hdd or RAM stick or Mobo), so they try to fix the software, over and over and over.
  They go through much of the stuff you have and of course more if your are getting BSOD error codes which require dump analysis; but most of these are correctable if you start with testing and fixing your hardware FIRST, and then if the software misbehaves, going through the software troubleshooting decision trees.
Here's the deal: 
 "NO SOFTWARE ON THE PLANET CAN FIX BROKEN HARDWARE!! PERIOD!!".
If you can accept this statement, and move on with testing your hardware, you can get your problem fixed.
  Having 3 degrees in Computer System Electronics and Design and 44 years in the Industry, I'm telling you this is the best way to troubleshoot your system; I've been doing it for many years successfully and have made a good living doing so.  Of course, you can do whatever the heak you want with your system.  Advice you get from folks like this on this forum is as good as it gets; and you've been here for awhile I see, so you get that: that's why you're here asking for professional help.
 
So, stop focusing on fixing all your problems with software solutions, and test your Hardware!!  Replace failed components as necessary.  If you go through all my steps, especially the link in my 
Post #2 to HW & SW testing, this will result in a fixed system more than likely.  People often ignore this advice, and spend weeks or months trying to fix their Windows build, and tell us that it's too much work to test their hardware, too difficult, and of course they often don't believe us that it will fix it.  Sometimes, they give up, trash their entire system and start over (a very drastic step!), or replace their Motherboard--but the problem often comes back, especially if they re-use a failed (or non-tested failed hdd) hdd from the original build on the new Mobo.  All the same problems come back, and often more, as they build the new system and don't take all the necessary precautions--such as checking their PSU ratings, cables, other stuff that a shop tech would always go through.
 
Enough on the lecturing; can't help it; I'm also a teacher; what can I say?
 
If you're willing to take a few days and go through everything I've provided to you, you should wind up with a fixed system.  If not, you can always scrap and rebuild a new one that works properly from scratch, or take into a good repair shop and 
PAY them to fix it for you!  DIY guys like us hate to do that--not because we can't afford it, but rather it's a pride issue; we can't accept the fact that something was designed wrong from the git-go, or that a piece of hardware broke.  What's the big deal?  If something in your car breaks, and it doesn't go--you troubleshoot it, find the bad part and replace it.  If necessary, you pay a mechanic to do for you if you don't have the right tools, knowledge, skill, etc. and soon your car is driving again!  Take a few minutes, step back, and think about what I've said here; take a deep breath, and then think about what I'm telling you and you can get this computer on the road again!
 
Post back your 
HDD, PSU, GPU Card specs, and that will help us to guide you further.
 
Best, 
<<<BBJ>>>