I don't own one and that's a bad photo, but from other photos on the net I figured that's a power supply bypass capacitor for the 74ACT08 AND gate right next to it. The capacitor value is not that critical, it most likely could be 10nF or 100nF, and such capacitances are next to impossible measure unless you remove the capacitor from a working board and connect it to expensive capacitance meter capable of measuring such small capacitances.

You could put a same sized and same looking capacitor from another broken device maybe, just take one from near a chip.

But based on the symptoms I suspect the problem is something far more serious than a single missing bypass capacitor.

Thx for the extra effort Jepael.

I tried to put a 100nF on it to see if that did anything before your post, cause I figured something like that too.
But after a few minutes of success, the artifacts started to appear again and during windows installation I got a black screen once again...

I know tried different systems already and different power supplies.

I also removed the heatsink and replaced the extremely hard substance which would have passed for heat transfer paste back in the day, for something more modern to see if it was heat related.
Sadly, the same result.

I am a bit afraid this would be some BGA issue. cracks in the solder joints of the memory chips.

Have you tried downclocking the card. It may help