Slow shutdown one night and now a Disk is missing

I opened the case and had a look at every cable connector and pushed on them all, no loose ones at all, all very firmly plugged in. Once that has all been checked I plugged the computer into the UPS and hit the power on button and it's still completely dead, no signs of life at all.

If I dig out a really old AGP computer that still works from the spare bedroom and plug it into the UPS successfully that'll prove the UPS is working nicely, And then I can swap the PSU from the PCI-E PC into the AGP PC (providing all the cable specifications haven't changed?) and then plug all of that into the UPS that will then prove that the PSU is still working.

That's some progress right? If I can do all of that then it means the problem HAS to be with one of the remaining pieces, Motherboard, RAM, Processor

Does this sound like a decent plan?

I don't seem to have a button like that anywhere on my board, There's an area where there are printed words that say "Ez Debug LEDs" but I have no idea if they work as I haven't tried plugging it in with the side panel of the case off
https://asset.msi.com/global/picture...s_RGBCover.png

this is what i'm working with.the EZ debug LED bit is written roughtly where the button is on your picture

phew, well I read up about the primary slots and followed your instructions, the first set didn't see the computer start, but because I had the case side panel off and was looking directly inside I could see that the graphics cards fan moved a little.

when I went to test the second set of sticks though more lights and fans moved for a split second but a small cloud of black smoke came off the motherboard followed by a very very strong burning smell, I decided to unplug and stop testing immediately.

I drew a red box in MSpaint roughly where the smoke come out (vision blocked by the graphics card), but I think it's time to buy a new motherboard and grab a refund on this one!

Motherboard arrived and I hooked everything up meticulously, made sure all my cable routing was perfect because I thought this would be it.

PC is somehow even deader than before, where as before when I looked inside while powering on something somewhere always lit up or a fan moved a tiny bit, now it does absolutely nothing.

The orange network cable LED showing power to the motherboard and cable plugged in is the only thing that works at the moment.

I've tried unplugging and reseating the 8 pin CPU cable, unplugging and reseating the 24 pin motherboard cable and because a eerie absolute nothing was happening I tried unplugging and reseating all the front panel cables.

The place I brought it from sent an email after purchase saying they open the motherboard box up and check the pins before shipping and any bent pin based returns will be the customers fault, I wasn't too happy they have people opening my product and poking around in there but there is nothing I could do about it.

I was wondering if it was the motherboard battery, but the last time I had a bad battery the motherboard worked but just didn't keep the right time of day on the clock.

or have I bricked the RAM in the last test or ruined the Processor when I removed it, I'm at a complete loss again.