[SOLVED] New Components, No POST

[Fragaroth]

Hi all,
Recently I have upgraded a crappy pre-built PC by replacing every single part except for the RAM and the GPU.
However, over the past couple of weeks, my PC has not been booting, and my motherboard makes 5 short beeps.
I'm pretty sure this means CPU error, but the thing is, I have already gotten my CPU replaced, and it is working perfectly when I boot the PC without the GPU.
What is so strange, is that I've ruled out the idea that the CPU is the problem and therefore can confidently say that the GPU is the problem. But when I plug the GPU back in, why does the beep code say that the CPU is faulty?

My specs are:
GPU - Galax GTX 1060 6GB
CPU - i3 9100
Mobo - Gigabyte B365M (HD3)
PSU - Be Quiet! Pure Power 11 600W Gold Rated
RAM - Not really sure what this is, but the PC works with it so...?
Storage - MX500

I'm pretty much convinced that the GPU is the issue, so I'm planning to grab a RX 5500 xt, but I would love to hear some thoughts on what the issue is first.
Any help will be greatly appreciated!

 

[SteveRX4]

Is the old ram listed in your new motherboard memory QVL?
If not, then it either hasn't been tested or it's been tested and failed.

Same with the CPU - is it listed as supported by the motherboard on its cpu support list?

Beep codes are found here - https://www.computerhope.com/beep.htm
If it's a Dell then change your cr2032 motherboard battery.