PC doesn't POST (no beep code at all) but lights and fans on - If I remove RAM I do get "no RAM" beep code

The title explains a lot but I'll try and explain more what has been happening here.

I turned on my PC yesterdays normal and it went straight to windows 10 bluescreen with stop code 0xC000021A (STATUS_SYSTEM_PROCESS_TERMINATED). I let it get to 100% and restart and it went straight back into the same blue screen.

I let it restart again into Automatic Repair which did nothing (as usual) and then took me to the recovery center (whatever it is called). I tried to boot into safe mode but got the same 0xC000021A BSOD. Next time it did Automatic Repair it decided to scan C:\ but this just got to 100% and then restarted back to the same BSOD.

Next time I got to the recovery center I oppened Command Prompt and ran chkdsk /r and sfc /scannow, both didn't report any issues with my SSDs. Restarted and got the BSOD again.

I tried to Reset PC 'Keep My Files' option and after about 20s of "getting things ready" it just stops telling me it couldn't reset my pc.

I really don't want to have to do a clean install because I did some quite important work on it the evening before and stupidly didn't run my backup before shutting down for the night.

So, I created a Windows 10 bootable USB using this link to the official site. I booted off the USB and choose 'Repair an Installation' (paraphrasing), I ran chkdsk /r and sfc /scannow on C:\ drive from there in case it makes a difference to run it from the USB if that makes sense, again no issues found.

I couldn't find anything else in the bootable USB's recovery center that would help. Automatic Repair did nothing and there was no choice to reset pc (I guess because I was wasn't running the recovery center from the drive with a Win10 installation?). I thought by having a recovery USB, the recovery center would have the option to repair the corrupted boot files in my Win10 installation? Is that not something that can be done?

Anyway, I thought I'd strip the PC of anything not needed so I'm left with just the motherboard, CPU, PSU, GPU and RAM. I booted up, same BSOD. I thought I'd make sure it wasn't a hardware issue so I re-seated the GPU and the RAM. Same BSOD.

Then I removed one stick of RAM and this is where it got weird. No POST, no beep codes, nothing. So I switched the sticks (I only have 2 sticks so I replaced the single one with the other one I had removed), same thing, no POST, no beep code. The lights are on the motherboard, the fans start up when I press power but it doesn't POST.

I decided to remove both RAM sticks to see if that would do anything and thankfully I got the beep code that means "no RAM detected". I put both sticks back in and again, no POST, no beep code.

I tried googling around for this scenario but I could only find people saying that the lights are on, fans are on but they get no POST or beep codes if they have RAM in the motherboard AS WELL AS if they remove all RAM. This is different to my situation because I am getting the correct 'no RAM' beep code when I remove RAM but nothing when either or both t sticks are in.

Does anyone have any advice or have been in this position themselves? Thanks in advance for any help!

Seems like a system failure to me. First you should rebuild the files responsible for booting the OS. Open a command prompt and type the following:

• bootrec /fixMBR
• bootrec /fixBoot
• bootrec /rebuildBCD

If you still can't boot after this, then there is a another solution that I haven't tried yet, but should do the trick.

Troubleshoot/ Advanced Options/ Startup Settings and click Restart. You'll see some options, you have to press the number of the Disable Driver Signature option (7 I think).