Question Please help, GPU problems after installing M.2; black screens, POST screen freezing, error light on mobo

[xWinterSolstice]

So this has been a conundrum from start to finish, and I'm unsure if anything I did caused it, or if it's just an unfortunate coincidence. My friend gave me a Sandisk X400 M.2 M+B key. I opened my computer to install it. I had to remove the GPU to gain access to the appropriate slot. I noticed my CPU heatsink was very dusty. So while I had the case open, I decided to clean the heat sink and change the thermal paste. I accidentally got the tiniest bit of thermal paste on a couple of pins. I took a soft, unused toothbrush, doused it with 70% isopropyl alcohol, and gently cleaned the thermal paste out of the pins. I got all of it that could be seen with a naked eye. I sat the CPU in front of a desk fan for about an hour to let the alcohol dry up. I reinstalled the CPU, applied the thermal paste, and installed the heatsink. I installed the M.2 I was given. I reinstalled my GPU. Then when I powered it back on, I got a black screen, and the VGA light on my motherboard stayed lit. The GPU powered on, but was not displaying. I started troubleshooting. I rechecked my power cables, I reseated the GPU multiple times (I have not tried a different slot yet because it's in my best PCIEX slot, and it's physically too big to be brought down lower to a different slot), I tried a different PCIEX slot, I removed the M.2 I had installed, and I disconnected all drives and peripherals aside from my boot drive. Now, SOMETIMES it will boot up, but it's hit or miss. I've still been getting the VGA light on my motherboard, and if it does manage to post, it freezes on the post screen for a few minutes before finally starting Windows. Something happened, and I don't know what. I have not yet been able to test my GPU in another system, or another GPU in mine. I don't even care about the M.2 at this point, that is no longer the priority.

Is my GPU going bad? I thought one of the PCI pins on it was damaged because it was shorter than the rest, but I've been informed that's normal. Is my PSU going bad and becoming unable to power my components? It's 8 years old, but it should've been fine after disconnecting all the non-essentials, if that were the case. Is my motherboard going bad? Is this related to the thermal paste I got on my pins earlier?

Someone please tell me what my next step is, I've done all I can think to do short of testing components in a different system. Specs in my signature line.

 

[Deleted member 362816]

Never use 70% on electronics 90% minimum, to much water in the 70%, How long did you allow this to dry out before you turned the pc back on?

 

[DSzymborski]

Do you have another PSU to test? This was a pretty lousy one in the first place and should have been replaced years ago.

 

[Cyberat_88]

Cheapest way to find out if the NVME M.2 your friend gave you is defective is to buy another PSU. Also, for gaming purposes, the M.2 will do NOTHING in performance vs. a good running SSD (Samsung EVO/QVO/PRO).