by Willy - 3/19/12 8:14 AM
I can't give a definite answer but find this happens quite often. In fact as techs, calls to such problems are common. Yet, when the tech boots up the PC it just goes away. More importantly, the problem doesn't return or get a call back. Basically, you consider this a fluke and leave it at that. No one is going to pay to actually find the issue but get the PC going. It's far cheaper to replace parts and leave once its running.
Understand, while a PC is somewhat complex, these are running components that require little in voltages and minor amps and the PSU is core to get it all going. Even, under stress conditions it will do fine until it poops out. When all is said and done, OEM based PCs are build to mirror their needs thus various models out there. Those PCs that become stressed and they will generally under the "logical boot sequence" depend on the events of power-ON to happen. If not meant, refuse to complete the cycle. The results can be confusing at least but generally speaking a repeated attempts do result in a good boot. Which in turn suggest a bad PSU or faltering one. The other half is the mtrbd. which house the "logical ckts" and again if less than desired will refuse to boot. I like to think the "uuphf" isn't there or a weakness becomes apparent. Those PCs that house top-end GPUs also will partake in poor booting. they require alot to get going but once booted, generally will reboot on demand unless too stressed. Again, notice the pattern that a basic PC if put into stressful conditions may falter. At the same time, PCs that are left alone and ONLY do basic operations, will after time falter too due to wear&tear as they age, they're less than they were when new. PCs offered today are simple and build for less cost as possible even if of qulaity alot has to work right and often. Even the most expensive build PC still uses off-the-shelf parts, these are not the computers in the world of main frames past and alike. Think of of the typical PC as an appliance and you'll see where it all leads. IMHO, I offered this scenario for your quest. Otherwise, since you mentioned you were a tech, get the test devices and scopes and tear it all down and find the cause and rely it to us.