I have no idea what is happening to my pc

I have been wrestling with my cpu for days and I just can't get it to work. Here is my problem:
I was using my computer when it hanged suddenly. So I press the "power" button to switch it off. The next moment I try to turn on my pc, all i get is a black screen, not even POST. Some other things to note, My "power" led shows a yellow whereas my "hdd" led shows a red blink for 1 seconds and then nothing.

What I did:
I tried resitting all my mobos, ram, etc and cleaned it too but it doesn't help. Both the fans(PSU and mobos) is running though.

 

It's an intel brand. I tried what you said but nothing comes on. It will only comes on if I press the power button and release it but then the problems I mentioned will be present.

 

Sorry I didn't mean to double post but I cannot see where the edit button is. I don't understand what you mean by computer type. I try to describe my computer to the best of my ability. My cpu is at least 5 years old while my monitor is only a few months old. I think I better stop here because what I give will be too general as I don't know how to find the specific details of my system. I have 2 IDE slot.