- RAM test.
- PSU test. (Under load!)
- CPU test.
- Different cable. Different monitor. To be sure.

It can also be the specific slot going bad.

These are extremely complex circuits and something as simple as a capacitor starting to lose capacitance can cause a variety of issues that seem completely random.

Also, make sure everything is clean. No accumulation of dust anywhere (including in the PSU).

I mean a CPU stress test.

PSU should get used heavily during a CPU stress test. You can throw a volt meter on it, or failing that, use one of those motherboard monitoring tools. But I rarely have luck with them getting the voltages correct since all of them have their own calibration offsets.

Changing the motherboard might be crashing because you're using the wrong drivers if it's the same HDD/installation. Try safe mode for starters.

In rare, sad cases, putting the defective card into a new motherboard fries the new slot as well. But hopefully this isn't the case.

[edit] Don't forget CPU temperature.

I'd assume it could be a combination of factors taking in to consideration the fact old GPU made trouble in a another PC, & new GPU made trouble in old mobo I'd assume both could be at fault. Not like it's of any help. Though another thing that I suppose can get wrong which nobody has mentioned here, is some NB fault. Or some connector issue in the mobo(GPU) which damaged the GPU's(mobo's) connectors.

Sigh, I did not fix anything. I kept hoping it was a driver issue so I kept wiping the current drivers and installing progressively older drivers. No luck. I then got a hold of a different PSU in the off chance that mine was bad. Still nothing.

So to recap. Original video card stopped working so I bought a new video card. That fixed the artifacts but the driver kept crashing at boot. So then I used a different mobo. That didn't fix anything. So I thought maybe the PSU is bad since its 5+ years old and used a different one. No dice.

My roommate's old gtx 250 is working just fine so I'm currently using that. My best idea is that the original video card died and then the replacement was DOA. Seems unlikely but that's the best case scenario.

Unless someone else has a new idea after reading this post.

Bam: Oddly, my usb stick with Ubuntu refuses to work. I've put Ubuntu on it twice but I still get an error(I forgot what) that freezes my PC. The stick itself isn't bad I think since I've used it before.

Edit: Of course now my friend's video card which was working just fine before is now randomly displaying lines across the screen and other artifacts from time to time.

Sounds like the monitor is kaput tbh.