Computer will not boot(powers off immediately)

[Melvin_Parker]

Hello. I was directed to your forums through good; I found a chap with a similar problem but I guess the solution for him was not exactly what helped me. I was impressed by your forums level of expertise and how they aided the user.

Now to the problem

The other night I reformatted my computer, reinstalling Vista as usual. I usually have my power settings set to not hibernate/sleep but I had not the chance to change that. I had to leave to go to the store. When I returned the computer was in sleep mode; one or two lights were blinking on the computer(So it wasn't entire powered off.) I quickly moved my mouse and clicked to start it up. I heard the computer powering up like normal, but then it just turned off. I pushed the power button to restart it and nothing happened. I disconnected the power from the computer(unplugged from wall) , and reconnected it. I pushed power and the computer powered on for one second, and then just turned off. No image on screen, no beep/error sounds. Every failed attempt at starting the computer requires me to unplug and reconnect the power supply to the outlet. I have not been able to start it even once since this issue showed up.

My computer has an AMD Anthlon 64(forget the exact designation), 2.4GHz, single core
My motherboard is somewhat old, using AGP for graphics expansion
Soundcard is a Realtek, already tested and not the issue.
I have two sticks of ram, one being 1 gig and the other 512. The 1gig is a Kingston, the other I do not know
A 150 GB HDD is installed in my computer.
Radeon X800 AGP with 256 Memory.

Methods I have tried to resolve this issue;
1) I tried changing the voltage on the back of the PSU, just to see what affect it would have on the computer, nothing really worked when that happened. Turning it back and pressing power would power the computer, and then turn off a second later.
2) I removed the ram sticks, one at a time and experimented with ram combinations. The computer still turned off the same with no affect. With no ram installed, it managed to get a beep out before losing power.
3) I had removed the graphics card, and for some reason my computer will not power up(at all) without one installed.
4) I looked at the capacitors on the motherboard to see if any had domed over or outright exploded(read; leaked.) and none seem to show any sign of decay or degredation. They look brand new.
5) I had tried disconnecting one wire at a time and tried to boot the computer that way. I had no luck until I disconnected the Molex connector from the motherboard. The computer is powered up, but the led's arn't flashing and it just sits there. Also, removing both the Molex and the graphics card got the same affect. Switching the monitor to the onboard video does not do anything in any situation.
6) I have disconnected the heat sink from the CPU, am going to clean the thermal paste and reapply a new paste. I'm going to reconnect the heatsink and see how that goes.

I honestly have no idea what is happening with this computer, and why it just suddenly decided to poop out like this, but any help would be greatly appriciated.

-Melvin K.
Sorry for any grammar and spelling issues in my post.

[Melvin_Parker]

Just an update; I have taken the heatsink off the and cleaned away any of the dust that may have built up on the thermal paste over the years. I reattached it and the computer is doing the same thing still; no affect.

So, what else can I do? I'm not the smartest with computers, and I don't know what else to do. Any help or suggestions are welcome

[Dax_Brandy]

have you tried putting in a new power supply?

[Melvin_Parker]

We just did that last night. Worked like a charm. We are going to purchase a new one today(as well as pick up some thermal paste so I can reapply the heatsink properly)

[Dax_Brandy]

Good for you. Careful with applying thermal paste. putting too much paste is not gonna do good also. Just put a small amount and spread evenly on the surface of the processor heatsink. use an old credit card/ATM card to spread the paste.