Random no-post boot problem - any ideas?

[Art]

I'm trying to help my Dad troubleshoot a boot issue he's getting with a DIY system (specs at the bottom).

Sometimes it boots up perfectly well and works fine, sometimes it doesn't. When it doesn't, after pressing the power button the fans and the SB power LED on the mobo come on, and you can hear the HDDs spin up but there's no read-head noise. There's no post beep when it fails, and nothing comes up on the monitor: just a blank screen. You have to hard-reboot it to get it out of this, and it doesn't always boot up fine afterwards: sometimes it can take 8 or 9 tries to get it to work again.

We've tried:

- Swapping out the graphics card for a new one; no joy.
- Updating the BIOS; didn't help.
- Googling it. A few people had the same problem and fixed it by manually setting the memory timings. Tried that, hasn't helped.

I'm currently running Memtest on it, and if that doesn't pick up anything I'm going to remove everything but the bare bones and start from there. I was just wondering if you guys have any suggestions/ideas that might save me a wild goose-chase.

Spec:

- Intel Core2Duo E8400 with stock cooler.
- ASUS P5K3 Deluxe Mobo
- Gainward 8500GT 512Mb
- 4x1GB Corsair XMS3 DDR3 1333Mhz
- Zalman 500W PSU

No overclocking.

 

[Art]

Yeah, I was going to try that after Memtest is finished. That'll suck if it's the issue though, that RAM wasn't exactly cheap. He's considering a new mobo though, so I guess if we don't get the issue solved it'll be expensive either way (especially if it's not a mobo issue..!).

EDIT: Memtest came up clear, but had the same issue with just 1 RAM stick. I was about to swap it and try a different stick but decided to try something else: I took out all of the RAM and tried booting it. The machine hung again, and there was no BIOS error code for the lack of RAM. I'm taking that as a sign the BIOS just decides to throw a hissy fit now and again, and that the mobo is faulty. Time for a new one methinks. Returning the old one might be a bit difficult though, we got it from Komplett which closed it's UK sales site over summer...