Only able to boot in safe mode; constant blue screens/restarting

That's what I've been thinking as well. When I look at the card, I don't see any obvious problems (fans are running). But, like I said, it is 4.5 years old and has seen pretty intense, regular use--and, I smoke cigarettes indoors next to it (I get the system professionally airdusted with a compressor, but I know that probably shortens its lifespan). So there's a bunch of dust buildup in the fan system, or it could have just crapped out naturally.

Again, I'm the only one in my friend group with a custom-built PC. They all use laptops or pre-built compact PC's that I wouldn't feel comfortable busting open. There is a local PC shop nearby, I guess I'll try to sell it like: "If it's not the graphics card, I'll pay you to diagnose it." Meanwhile, I'm just going to order a new card on Amazon--'tis the season, right? Is it possible we could get a fresh set of eyes on this thread though--just in case there's something obvious we're both missing?

Oh my goodness; I hope I didn't keep you up. Thank you so much for all your assistance thus far, Lifetec. The local BestBuy actually has a GTX 1080 in stock now, so we might be able to settle that question once and for all in a few hours (it's only 7:00 pm where I'm at.)

I have a generic PnP Samsung monitor, it's about 27 inches I think and it's max resolution is 1920 x 1080 (the resolution I'm currently using). The purpose of my new card is to future-proof the system a bit; I've been wanting to play Titanfall 2 and Rise of the Tomb Raider on higher settings. I think you're right, in that now my processor/mobo/monitor are bottlenecking the system, but I had a little cash lying around. Just curious, what resolution do you think would justify a GTX 1080?

Full disclosure, I did go out and buy the GTX 1080 and install it last night and the system has been working like a dream ever since; installed flawlessly (I think, in part, due to that tip about the control panel setting so Windows wasn't trying to install updates at the same time.) Again, thank you so much, Lifetec. Assuming everything is still hunky-dory by the end of the day, I plan on marking the thread solved.