Computer Boots Black Screen

[Mimics]

So when I got home today I went to use my computer and it just has a black screen, there’s no motherboard screen or anything, and also my keyboard lights won’t turn on so I know it’s not just an HDMI or a gpu problem, other issues that I noticed is the power button isn’t working(even if held it won’t shut the computer off) and my hard drive won’t spin right(keeps stopping in this pc but working fine in others).

So basically I’d imagine it’s either my motherboard, power supply or maybe ram (not sure if the ram would cause the mobo screen to not show up but just threw the idea in just in case)

any help on this would be really appreciated I just need to know which part gave out so I can replace it, I just don’t have any other parts to swap and test with

 

[CountMike]

Kinda difficult to even guess as to cause without any part details but could be as simple as start button or everything gone to hell. By carefully reading your hint's, I would tend to blame PSU first.