Macbook Pro (Mid 2012 15 inch) crashes randomly

Hello Apple Support Community! This is my first writeup here so be patient with me.

In August 2012 I purchased my 15 inch mid 2012 MacBook Pro with 4GB of RAM and a 500GB Hard Drive. For the first 2 years, everything was fine.

Fast-forward to July 2014. I started school at a local university and brought my laptop with me nearly every day. (It got moved around a lot) Also, I had some money saved up and decided to purchase some more RAM for my computer. I purchased 2x4GB of PNY RAM and installed them. A few days later, a curious problem began to show up. Every night I shut down my Mac, but now every few shutdowns it would give me the little spinning wheel and would never shut down. I figured it was not a serious problem as it did not happen that often.

My problems didn't end there, however. During a software update to 10.9.5, the computer froze while shutting down with the same symptoms as above. I had to hold the power button to shut it down, and when it turned back on after the update, my bluetooth was gone. After an SMC reset, my bluetooth was back.

At this point, I was getting a bit worried about my Apple software and decided to Boot Camp Windows 7 onto my hard drive. And then Yosemite came out, so I installed it. Mistake.

Almost daily, I was seeing kernel panics galore. It did not really seem to matter what I was doing, all it had to be was on and it would fail. Windows 7 exhibited no problems when running, so I assumed it was a software issue. About mid-november, I wiped the mac partition of my hard drive and clean installed Yosemite. For about a week, I thought my problem was cured. Then the crashes returned again. I switched back to my factory installed memory thinking that it may have been a bad ram stick. Once again, okay for about a week then crashed again. I put the 8GB back in again because I would rather have a fast and crashy computer than a slow and crashy one.

Also, weird graphical glitches began to happen. On certain occasions, when starting up things like Java or even doing something as simple as going to Yahoo!, the discrete NVIDIA graphics card would activate. Sometimes, it would quickly flash the screen completely white or blue then go back to normal, and occasionally the entire screen would freeze except for the mouse, which would only go away by holding down the power button and resetting. Doing a NVRAM and SMC reset, once again, would work for about a week before it would crash again. Also, when plugging in my hard drive for backups, it would refused to eject the disk. I had to hold down the power button to get it to eject (For most backups, I had to resort to booting in Safe Mode, as Safe Mode would actually eject the disk when I told it to.) These panics are not consistent, mind you. They have happened during start up, once during shutdown, but mainly during low load situations after the computer has been on for a while. Oddly, it is most stable when running at high ram and the fans are blazing during gaming. It has also never crashed when a virtual machine (Virtualbox) is running either.

A couple of weeks ago, it completely melted down. The system crashed, then restarted, then crashed, then restarted, then crashed, then (you get the picture). Completely, panicking at this point I tried to boot into my windows partition. It got to the Welcome screen, but then went black and the hard drive started making a really high screeching noise, at which point I shut off the computer and scheduled an appointment with the Genius Bar the following day.

At the Genius Bar, I told the Genius what was wrong, and after playing around with it, reinstalling the ram, and getting some error messages, he gave me the following diagnosis: A bad partition of the hard drive between Windows and OS X and improperly mounted RAM. (Oddly enough, when we remounted it, the directions he gave were different then those on apple.com). I hooked my Time Machine back into my Macbook, and for a while it looked like the fix worked. No more kernel panics or stalled shutdowns.

A couple of days ago, the stalled shutdowns returned, and today it has crashed twice on me (once in Safe Mode). I'm at a loss. I've checked so many different things from websites that it is making my head spin. I use my computer for school every day and need it to be reliable. Considering that I have only gotten about two and a half years out of a $1700 computer, that is absolutely pathetic. I really would like this computer fixed, but I do not have money just to throw around. Does anyone out there have any ideas? Let me know if you need more details.

Thanks in advance!