What happened to my 1 year old build?

[lolhard123]

Ok so here's the story from the beginning.
A few days ago I tried turning on the pc and I was surprised to find out that it gave no signal so, I went ahead and unplugged the dvi cable and plugged it back in and restarted the pc and voila! It worked. This kept happening to me everyday I tried to turn on my pc but I ignored it thinking that it was the dvi cable's fault well, yesterday non of the above happened and I was happy to see that until, my cursor started lagging all of a sudden then bam! no signal and the GPU's fan started spinning at its max speed so, I turned the pc off and here's what I've tried so far with no luck.

Try another cable and another monitor.
Unplug all the power supply cables and reconnect them.
Remove the graphic card and reinsert it (for some reason after doing so the gpu's fan stopped running at max everytime I tried too boot up)
Try the ram sticks In every possible combination.
Unplug the harddrives and the optical drive.

Currently here's what happens when I try to boot:
The cpu's fan starts to spin for a few seconds then stops for a few seconds then starts to spin again.
The led lights on the motherboards light up (1 red 1 orange or yellow and 2 green) they stay on for about 15 seconds then turn off.
All the other fans function properly.

Specs:
Cpu: i5 2400
gpu: sapphire hd 6950 1gb
ram: 4gb kingston value ram 2 sticks
mobo: gigabyte pa65 ud3
psu: antec neo 620w

Any thoughts?
Thanks in advance.

 

[jitpublisher]

First thing I would suspect is your PSU.

 

[lolhard123]

First thing I would suspect is your PSU.

I thought so too since my father's pc had the same psu and it failed 2 days after the build. But how can I be sure of this?
Edit: Here's a video showing the pc failing to boot: http://www.youtube.com/watch?v=EqsYFw104zk&feature=youtu.be

 

[lolhard123]

Also I forgot to ask, could I possibly disconnect the 24pin and the cpu 4 pin of the cpu from my father's pc and connect them to my motherboard and see if it posts? Could this be used to know whether or not the power supply is the problem?

 

[geofelt]

Since you were running ok before, something must have failed.
That is unusual once the "infant mortality" failure time period has passed.

I think the most likely suspect is the video card.
Is there another one you can try?

Are all your power connections secure? Particularly to the video card.

Antec is a quality psu, and it is unusual for such a unit to fail.

 

[ram1009]

There's only one way to troubleshoot a PC problem like this outside of a laboratory environment. Replace one componenrt at a time with known good ones until the problem goes away.

 

[lolhard123]

The only other graphic card I can try out is the one present in my father's PC. I'll try and give that a shot but I really hope it is't the problem.
Thank you both for the replies.