The only reason i ask is because i have a strange problem that happens intermittently with my ageing (8 year old) pentium 4 machine.

You can be working away, or maybe come back to it after doing something else and the entire pc will be frozen, locked up solid, mouse doesnt move, no buttons press, even numlock capslock doesnt register on/off with the little LED on the keyboard, whole thing totally deaded.

However, what i have found is, after getting in a mood and giving the side of the case a moderate thump in anger, that if the case is hit on the side, which makes it bash into the wall, the motherboard beeps and then the PC miraculously comes back to life again, very odd.

But then the other day it just would not boot up at all, system disk something or other error, just hangs at the 'detecting ide drives' section of bios then errored, so i hit restart button, it did it again, stuck at detecting part, i thumped the case, and off it went, all detected now, and into windows it went.

However, what i have come to notice when it goes and freezes, is that the machine itself gets quieter just before it locks up, and when doing this slightly odd proceedure to get it going again, is that as the mobo beeps, stuff in the case gets louder, and i have done this with the case open, and what the louder sounds are, are the hard disks spinning back up again.

So they are obviously losing power, and it cant be a faulty HDD unless they are both nackered, because HDD1 and HDD2 both go off and come on when the case is given a good clump, so my guess is a faulty voltage line/switch mode in the PSU that runs the drives, i know that fruit machine PSU's have this as a common fault, (+5v line always breaks on those, got 4 dead ones here lol) so is this a known issue with PC power supplies also, as i have checked all wiring and connections etc, and everything is as it should be, so the PSU is the only thing i can think of.

Many thanks in advance!

instead of beating the crap out of your hard drives, why not try changing the power supply for a while and seeing if it does indeed fix the problem?

like any mass-produced item, some power supplies can be crap. but ram problems can cause lockups too, so at this point it could be anything.

Try setting HDD wait timeout to some higher value in BIOS settings. Sometimes 3 seconds (default value here) isn't enough for drives to spin up.

Quote from danthebangerboy :

Is PSU failure/fault a common issue with desktop PC's?

Yeah, PSU failures are fairly common (especially with cheap and/or older units). Often when people are building their own PC they choose to save a bit of money on the PSU (buying a cheap piece of crap) so they can spend an extra £20-30 and get the next fastest CPU/GPU or a bigger hard drive. The obvious reason (well, obvious to them...) for doing this is that there's no apparent or immediate result in buying a better power supply. When you buy a faster CPU or GPU you get a faster, more responsive machine. Buying a better PSU just decreases the risk of having a major failure (which can take out other components...), decreases the risk of system instability and can help with cooling/noise. The same thing happens with pre-built systems (it's easy to market a fast CPU but not a high quality PSU).

Your specific issue does sound like a power supply problem (general symptoms of PSU failure are system instability and difficulty in booting), and with an 8 year old PSU I wouldn't be at all surprised. What you can do to test it (and something I only learned about recently) is the "paperclip trick". That'll allow you to isolate the PSU and test it without any other components.