Win 8.1 and faulty GPU/Driver issues [Please Help]

Hello!

So I recently built a new gaming PC. This is my second build and everything went flawlessly. I installed all the hardware meticulously and the computer worked fine for a little over 2 months. Keep in mind that I have done no overclocking or aftermarket modifications of any kind in this rig.

Here are the essential specs:
CPU: Intel 4770K LGA1150
MOBO: GIGABYTE GA-Z87X-UD3H LGA 1150
GPU: EVGA GeForce GTX 780 Ti Dual Classified w/ EVGA ACX Cooler
PSU: SILVERSTONE Strider Gold Evolution SST-ST1000-G Evolution 1000W
Boot Drive: SAMSUNG 840 EVO 250GB
OS: Windows 8.1

Old GPU: ATI Radeon HD 5850

And a link to my build thread if you need/want more info: http://www.tomshardware.com/answers/id-1843730/2500-gaming-enthusiast.html

On 2/9/14 I was watching a movie, about ready to fall asleep. I got up to close the window my video was playing in, and upon clicking the close button, my screen instantly became filled with evenly spaced and alternating green and red vertical lines! I instantly did a google search and the first three posts I read, all mentioned that it was likely a problem with the graphics card.

Mortified, I instantly hooked up my monitor to my older PC and everything worked fine (eliminating the monitor as a suspect). I then contacted EVGA customer support to begin the RMA process. While speaking with the technician, he recommended that I install my new 780 Ti into my old rig to see if I still had problems. Unfortunately, I was unable to do so because of clearance issues. Contacting tech support again, I was told to just go ahead with the RMA.

So this brings us to today. When I got home from work, I decided I wanted to install my old graphics card into the new rig in order to rule out the motherboard/PSU as candidates (which is something that was mentioned by the EVGA technician over the phone). I did so, and everything looks fine. No "artifacts" or anything. I then decided that it would be a good idea (I thought) to uninstall all NVIDIA drivers, reboot, and install the ATI drivers. I was also thinking this would be good anyway, so that when I got my new/fixed 780 Ti back, I could install fresh drivers for that.

Immediately after uninstalling the NVIDIA drivers, I noticed that I was unable to click (right or left) the windows/start icon in the lower left corner of the screen. Because I had just read that after uninstalling old drivers a system restart was necessary before installing new drivers, I shut down the computer. Upon restart, everything worked normally until the windows start-up had finished. I was then staring at a completely black screen except for when I moved the mouse, in which case the mouse icon would appear for a moment and then disappear. The only way I was able to get the computer working (somewhat) normally again was to use my Win 8.1 OS disc and do a system restore to my most recent point. So now I'm back to where I was after initially installing my old graphics card.

So here are my questions/concerns:

1.) With what you've read, do you feel the green and red vertical lines are indeed the result of a faulty graphics card?

2.) While I'm waiting for the RMA process and considering that things seem to be working just fine with the old GPU, do I bother with uninstalling NVIDIA drivers and installing ATI drivers?

3.) If so, how do I go about doing that so that I don't end up with a black Win 8.1 login screen?

Any and all help/advice/criticism is greatly appreciated!

Please let me know if you require any additional information.

Thank you for your time!!!