Pre-POST Boot Problem

**The post will sound fairly long-winded as I've decided to detail my experiences with the issue and the various means that I have tried to troubleshoot the problem. The description will sound a lot like a HDD/PSU issue but it will make sense to be in this forum at the end**

I've got a problem that quite a few people on this forums have encountered -- The CPU being switched on and not executing the boot sequence at all. Nothing on screen, no sign of life on miscellaneous USB powered devices like the Keyboard and Mouse, but you hear the whirring from the CPU that sounds intense and does not die down, like it normally would. It takes a few reboots and switching off/on of the CPU before (by luck?) it works and boots up normally. No noticable error messages are displayed. Upon inspection of the CPU, it can be seen that the fans are working, except for the motherboard fan, which seems to spin up, then halt. Spin up and halt. A slight clicking noise can be heard, but no beeps.

For the TL;DR version, scroll to bolded portion at bottom.

There are a few common symptoms before this boot problem arises (split into mutually exclusive pts, unless listed split alphabetically):
1a. The usage of an external Hard Disk shows signs of power but is not detected by windows. It also causes explorer.exe to hang. A few normal restarts of the computer gets it to function normally.
1b. HDD gets detected and functions without any problems. After "Safely Removing" the device and shutting down the computer (without turning off the Mains), attempting to power-up the CPU causes the boot problem.
2. Windows suddenly hangs. (Can either be with a external HDD connected or recently ejected) No BSoD, no input captured by mouse / keyboard, monitor completely frozen. Computer will then fail to boot completely.

Solutions that have been attempted:
I first tried to narrow down the problem to make sure it was not a Hard Disk error.
- Testing of HDD on a separate computer -- Works perfectly all the time. Therefore, no faulty cable, no virus etc.** A thing to note is that on my other computer, it only takes 1 USB slot on the cable to get the HDD working. On my current computer, it takes 2 and still has a chance of not working.**
- Reformat of the computer. Thinking some bug might have been caught in the 1yr+ of no reformatting, I tried a full reformat. I also purchased a brand new 1TB HDD which I also upgraded my OS from Vista to Win7 on.
- Getting advice that booting issues are most commonly caused by a faulty / burnt out PSU (I leave my computer on through the night sometimes), and that many people with this problem have done the same, I replace my 550V PSU with a slightly superior 600W one.

Things start looking good. In Windows7, the hard disk although sometimes still undetectable, does not cause Windows Explorer to hang any longer. I begin to suspect that the USB ports at the side panel is having a problem powering up the HDD so no big issue, just a matter of using the rear USB slots.

A few days of use later however, the problem returns and I'm baffled. I find a temporary solution though:

Upon using an external device and shutting down, to get the computer to complete a boot sequence at the next startup, I have to perform a power cycle and/or discharge the electricity (switch off PSU and turn on computer) before the computer will boot properly.

How do I solve this final problem? I find it especially heart-breaking to have to replace expensive parts due to a small hitch like this.
5 answers Last reply
More about post boot problem
  1. No such thing as a pre-post boot problem. :)

    You successfully complete the POST, then the system - hopefully - boots.

    First, some computers just don't like external USB drives plugged in during the boot process.

    Your PSU has a problem in the standby power circuits. That's:

    the part of the PSU that is always on,

    provides power to USB devices (that's why your keyboard looks like it comes on, but because the rest of the computer is still off, nothing happens),

    and responds to the case power switch.

    What kinds of PSU were the original and the replacement?
  2. Hey jsc,

    Thanks for your reply.

    Heh, figured since it wasn't even booting to the POST, it would be called as such. Thanks for the clarification.

    A few misconceptions from my post:
    - I didn't plug the HDD in prior / during the boot process. Only once it has reached Windows itself. So far however, I've bought an external USB hub (w/ power adapter) and it seems to have resolved my HDD problems.
    - When the PC fails to show any response, the keyboard and mouse don't light up either. The CPU however has the fans functioning (thus the intensive noise), but does not transition into the next phase.

    So I reckon it's something to do with some kind of power outage thingy.

    My original PSU was an Acbel 550W one and the replacement a Vantec 600W one. It's odd that both the old and the new would exhibit the same problem. What are the odds it's still a PSU problem?
  3. /bump!
  4. I just purchase an ASUS M4A78-E with Phenom II X4 - and 2x2Gb of 800MHz after assembling everything and starting the computer it powered on - the disk lights come on etc but the computer wouldn't post - no beeps at all. I tried a different power supply and checked all connections. No luck. I stripped it down to just the motherboard and processor and monitor - it has onboard graphics (no memory). This time it beeped the code for no memory. I loaded one stick of memory and it posted and booted. I switched to the other stick and it wouldn't post. So it looks like a bad memory unit will cause the computer not to post without having the memory error beep.
  5. My memory checks out okay though. I've been able to troubleshoot the problem 100% of the time by power cycling now. I still want to resolve the problem however, as power cycling 3+ times a week gets quite frustrating.
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