UPDATE: This is very strange so I was giving up and was putting everything back together ram, GPU, nvme ssd etc and thought hell let's power it on again and boem it beeps and boots to windows... Only the HDD and SSD are disconnected still. Is there anything I can do to test the components or something?

I just fixed a computer that had the same exact symptoms. It had all started when a friend wanted me to transfer the guts of on pc to another. Everything worked fine before I started but when I was done I was in the same boat. First thing I noticed was that the Power button would start it but would not turn it off after pressing it seconds at a time. I didn't think much of it as that is a minute problem compared to the problem at hand so I forgot about it. Down and out because nothing on the internet worked. I narrowed it down to about 3 components that could be the cause. The Motherboard, CPU, or Power supply unit. There are others but i was able to eliminate them. Now back to the power button and why the pc would'n't turn off holding it down. It took me some pondering but I came to a conclusion that this was most likely a power supply problem but that isnt always the likely cause. I got out the voltmeter and started checking the power supply unit. I got to the 8 pin ATX Power connector on the Motherboard and had no power from it. Now I have looked up the symptoms of not connecting that power connector to the MB. This may include, No beep on startup, no video, fans and lights come on but nothing else doesn't. The wire actually had a loose connection at the Power supply. The fix was actually easy. I took that cable off and checked continuity of each wire and I didn't find anything wrong with it. There are a couple fixes, 1 buy a new cable or power supply depending if you can remove it or altering the wire to fit in the plug. ONLY do this if you know what you are doing and experienced. I am not responsible for what you do to your computer. I altered the wire because my friend wanted it up and running ASAP without having to order a part. To do this I cut the end of the plastic connector( the side that is most loose. Both sides may need it.) I took off about the with of a dremel cut disk. this allowed me to get a better connection with the pins. I plugged it back in and noticed it had snugged up quite a bit. Turned it on and it all seemed to work along with the power button now when pressed Turns it off. Sometimes it is finding those minute problems can be all the difference between fixing it or junking it. Check all your connections for looseness, have patience and eliminate items you know for sure have nothing to do with it. Don't give up or get discouraged. There are solutions for this issue

I always reseat my ram when this happens.

UPDATE: PC Powers On, No Display, No Beeps, Nothing · I have had this PC for around 2 years now, the base items I have acquired from Directron (Motherboard, Memory, Processor, Case). Over the last two years I have only made a few upgrades (Video Card, more Memory, Hard Drive). Most recently, I had to replace a dying fan stationed at the back of my PC (Thermaltake TT-1225). · The night prior to the issue starting, I was using the computer to play World of Warcraft than later Starcraft. I shut down the machine and went to bed. When I returned to start it up again, I encountered the problem. · Computer Specs: Asus P4P800-E Deluxe Motherboard Intel Pentium 4 3.0ghz Processor 4gb RAM Corsair CMX1024-3200C2PT x 4 PNY Technologies GeForce 6600 256MB DDR Graphics Card Creative Sound Blaster Audigy Sound Card Thermaltake X Silent Purepower 560w Power Supply · My computer will power up, all the fans will work, the hard drives power up as well. The CPU fan even spins. But I get no display and no beeps at all. I wait 5 or so minutes to see if my computer is going through its start up process and is reaching Windows which usually triggers my mouse and keyboard to light up. It did not reach this point and the only way I can power off the machine is by holding down the power button for 5 seconds. · I tested my current monitor and video card (normal arrangement), as well as tested one of the current with an older monitor and older video card, still same problem. No visual, no beeps, nothing. · I don't see the power light, lighting up on the motherboard as it normally does which leads me to think it is a Power Supply or Motherboard issue. I have checked all the connections and tried to load with and without pieces of hardware (Hard Drives, CD Drives, Sound Card), and no matter what I get the same results. · I tested a bare bone power up (Motherboard, Processor, 1 Memory Module, Power Supply, and Video Card), and still encountered the same issue. Upon inspection of cords and their input connectors, I noticed the 12v connector seems like it might have been burnt on 2 of it's 4 sockets. 2 of them look browned as if burnt and the other 2 look fine. I checked the motherboard connector for the 12v an it doesn’t seem like it is burnt but doesn’t seem like it would have been by the shade of the brown on the inside of the power connector. · This is the part hat has me confused. I don’t believe it to be a Power Supply issue when everything powers up when plugged into it. So I am thinking it is Motherboard or Processor since even in its bare bone form it gives the same issue. Now if it turns out to be an issue with the motherboard or Processor, will I still need to replace the power supply as well due to that 12v plug looking burnt on the inside of the plastic casing? · Any and all assistance would be greatly appreciated.