Question Unexplained errors

[Sparkster2348]

Backround:
6 Months ago I built a new PC and I have always had unexplained crashes during gaming every so often.
After doing extensive troubleshooting and replacing various parts of the PC, I attempted to RMA my 7800XT but they couldn't identify a fault.
Whilst my GPU was away for 7 weeks, I was using an old 260x, and experienced zero issues.
Throughout the months I had used the iGPU a few times when trying to test various things, it would always automatically switch to the iGPU if not GPU was installed.
I got my GPU back and the issues continued, so I decided to take it to a local repair store to see if they could identify the issue.

The Issue:
After taking my 7800XT down to the repair store I couldn't be bothered putting the 260x back in, so I just went to boot with the iGPU but it came up with the red VGA & Bootlights on the mobo.

I couldn't understand why the IGPU stopped working, so I just put the 260x in and updated the drivers and it seemed to work all OK, but I noticed MSI Afterburner was blank for some reason, I couldn't see the mhz, temps, tweak the fan curve, etc.
Google searches indicated that the drivers didn't install properly and I needed to DDU the drivers and reinstall them so I did.

After reinstalling I started having problems.
The screen was all pixelated and smudged, it kept freezing and going black, and I was getting some weird AMD driver issues popping up. (Although I could see the GPU in MSI Afterburner now).
I would switch to safe mode it would be fine, then I would try and clear the drivers and reinstall again and the problems continued.

Assuming the 260x was about to die, I took this time to try and go into the bios and force my motherboard to boot to the iGPU whilst I could still get display with the 260x installed.
Then it wouldn't boot past the mobo logo screen and came up with an error initialize library failed 0xc00000bb.

So I took the 260x out, put it it into another PC, ran it through stress tests and it worked flawlessly.

Went back to my main PC, cleared the CMOS, and now it lets me boot into the iGPU without any issues.

Obviously other trouble shooting occurred during all this, but you get the general idea of what occurred.

Whilst i am glad everything is working I am completely stumped as to what actually happened and how I fixed it.
I am now also concerned if I go to put back in my 7800XT once I get it back I am going to have the same issues as with the 260x.

My two main questions:
- Why do you think my iGPU wouldn't work until clearing the CMOS when it worked in the past?
- Given the issues described with the 260x, could my PCIE slot be faulty, if not, why is it having issues in this PC now when it didn't before?

 

[Lutfij]

6 Months ago I built a new PC
When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.

Sig space specs can and will change over time and when that happens this thread and their relevant suggestions(advices) are rendered moot to the user in the same boat as you're in now. This is why we ask users to pass on the specs to your afflicted build in the body of your thread.

Why do you think my iGPU wouldn't work until clearing the CMOS when it worked in the past?
Corrupt BIOS, perhaps.