PC Will Not POST - I'm dumbfounded...

[ahall52]

Need some help - about 6-7 weeks ago my main PC started locking up under medium processor load. I'm not certain that it had anything to do with processor load or not, but it was not exclusively during gaming or other high-load events. The lock-ups became more frequent over the course of a week or so and then even booting was a problem and would cause lock-ups. I've been without my main PC for 5-6 weeks as I have been troubleshooting and ordering parts and am completely sick of being in the dark ages. I need some help! Here are the details at the time of crash:

Motherboard: ECS nForce 570 Slit-A (v5.1)
Processor: Intel Pentium D 940 (3.2 Ghz)
RAM: Ultra 2048 MB PC5300 DDR2 (4x512)
Video: 2x PnY GeForce 8800 GTS (SLI)
PSU: Ultra 600w X-Finity

Aside from the HDD, DVD Burner and a cheap TV Tuner card, there wasn't anything else in the PC. After a just under a week of crashing, even getting the machine to POST was nearly impossible so after some basic troubleshooting, I started replacing things.

The first thing to go was the PSU. I thought that it was maybe sending some bad power to the rest of the machine so I replaced it with a shiny new 750w PSU, but no joy on that target. Still couldn't get the machine to respond.

Next I ordered a new CPU. I replaced the Pentium D (which I had planned to do a year and a half ago when I built the thing) with a new Intel Core 2 Duo E7400 2.8Ghz processor. No go.

I then purchased two (2) remanufactured motherboards identical to the original ECS nForce 570 Slit-A (v5.1). I have tried the new processor on both remanufactured MoBos and still no luck.

Additionally, I have done the following:

- Tested the machine with each stick of RAM indivudually.
- Tested the two video cards in a separate machine and they both work.
- Tested each of the configurations above with only one of the video cards (the motherboard does not have on-board video).
- Checked all of my connections MANY times.
- Reset the CMOS twice on each MotherBoard.
- Tested the original PSU to find that it is seems to be working fine.
- Reattached the original PSU to the updated hardware to see if the new PSU was the problem. It isn't.
- Checked all of my connections MANY more times.
- Have tried all of the configurations above without attaching the TV Tuner and have tried the most recent configurations with ONLY one working Video Card, the CPU & CPU Fan and one stick of RAM at a time - nothing else plugged in to the MoBo.

Also, the monitors are working fine and I'm a freak about good cabling so it's not an issue there.

I'm at my wit's end and need some serious help. I cannot for the life of me figure out why the machine won't POST. The only jumper on the Motherboard is the reset CMOS which is in the correct position. When I turn the power on, all of the fans turn on. A couple of seconds into it, the Video Card fan kicks in. And that's it unless the drives are plugged in and then they start whirring as appropriate as well. No beeps whatsoever (I think it's AWARD BIOS so no beeps is not necessarily a bad thing). But nothing changes on the monitor - it stays in it's connected-sleep state.

Could it be that ALL four sticks of RAM went bad at the exact same time and would that prevent a POST? I don't want to replace them without knowing that they are bad too as I have run out of money because the wife and I are saving for an adoption.

On the bright side, if I find out that I've missed something completely simple and fixable, I have just about enough pieces to build a new PC.

I would be grateful for ANY advice that anyone can give me as I don't know what to do...

[Sylvander]

1.
(a) Disconnect all unnecessary hardware leaving only the the following bare minimum connected at the beginning as follows:
PSU, mobo, CPU+heatsink+fan, internal speaker, keyboard
i.e. No video card or RAM.

(b) Ideally the mobo would be outside the case on a non-conducting surface to eliminate the possiblity of a short from mobo to case.

(c) If you believe the on-switch is functioning OK, use it, otherwise short the pins on the mobo to fire up the board.

(d) When you switch on, the POST should start, run, test, the 1st RAM test should fail [if the POST gets that far], and generate warning beeps.
If the internal speaker is functional you should hear those beeps.
That means your POST is doing what it aught.

(e) [Shut down, switch off and] Connect the video card, and switch on.
That shouldn't prevent the POST from starting, running, testing as before, and you should yet again hear the beeps of the failed 1st RAM test.

(f) Connect one stick of RAM in the 1st slot, and switch on.
This time there should be no beeps warning of a failed RAM test, but instead the RAM test should pass, the POST should continue and initialize the video card, you should hear a single short beep and see a display on the monitor.

(g) That should do for now.

[ahall52]

I never tried the old CPU in one of the manufactured motherboards - until now. POSTs just fine. Looks like either the new CPU isn't compatible with the Motherboard *OR* I got a bad new CPU.

Thanks all!