My computer sucks (Formerly "Critical overheating issue

[ZephixLeer (Zephic)]

Keeloth... Can I assume the "old HDD" was in this same pc, or at least hooked to the same mobo?

The cable or motherboard controller are now sounding highly suspect.

In fact, if what I'm understanding is accurate, so far you've had overheating issues, hdd read issues/hdds going bad, and although seemingly still heat-related, moving the GFX card to another slot seemed to alleviate the issues.

There are just too many problems here for it to be chance that you've gotten two bad hard drives and overheating issues that were mentioned as "having a history of" those problems.

Is it possible you had legitimate overheating issue that caused your original problems? Sure. Is it possible you had one bad hard drive after that? Sure. Is it possible you had a second bad hard drive after that one? It's possible, but getting more and more unlikely and pointing to something else being the issue.