PC switches off after boot

My PC has behaved perfectly since I installed Windows 7 several months ago.

However, around a week ago, it started to take a long time to recover from sleeping. The hard disk would thrash for 3-4 minutes before the usual log-in screen would appear. Then things would be OK.

More recently, it started to switch off after coming out of sleep/hibernation. Once rebooted it was OK.

Then today, it got worse. It switched off *every* time I booted past the log in screen - sometime at the log in screen. I have tried safe mode, removing all USB devices, but nothing now works. Every time I try to start my PC at, or shortly after, the log in screen my PC switches off.

I presume that this is a pretty fundamental hardware fault. Perhaps the motherboard? Although it is a quad core machine with 4Gb of RAM, it is pretty old (around 3 years) so I suspect a hardware fault of some kind and I am considering a new PC.

Any ideas about what is causing this problem? Is my PC finished?

Did you do anything to the computer just before your computer began to show the problems?

No. The problem started when my PC was slow to recover from sleep/hibernate mode. Then it just switched off and I had to leave it several minutes before it would restart.

I have been advised that it might be an overheating or power supply problem. Given that both CPU and graphics fans are working OK, I think it might be a PSU problem.

Is that likely?

It is always possible it could be your PSU,

Though at this point I suggest:

Computer Shutting Down Instantly & Unexpectedly - Many Event Log Errors

If anything matches, check solutions and see if it helps otherwise.

You could test your PSU on another computer or test a friends with your computer incase it definatly is a problem.

Though check here:

https://www.sevenforums.com/crashes-d...-problems.html

You may end up buying a new power supply

bobbyelliott said:

Once rebooted it was OK.

Hi

Is this still the case?

Regards

LATEST UPDATE: I used the Windows 7 repair disk last night and the PC went through the repair process and booted OK and worked for the evening. That made me think that it was not a hardware fault since the (non-Windows) repair DVD worked OK. But this morning, when the PC attempted to come out of hibernate, the problem returned -- the PC switched off at the log-in screen.

So I tried to run the repair DVD again (I was going to back to an old restore point) but this time the machine cut-out while running the repair DVD. So I guess it is a hardware fault after all.

I tried blowing out dust (there was lots) but the PC switched off when I tried to start it.

I now think it is definitely a hardware fault and likely to be one of two things: (1) a power supply fault; or (2) a memory fault.

I have two memory chips so I plan to remove them both and re-seat one to see if that cures the problem. I can swap the modules (one at a time) to eliminate memory.

Failing that, I'll buy a new PSU tomorrow.

Unless anyone has any other ideas?

One other thing I should mention. My PC does not reset - it switches off -- instantly. It's dead. Nothing. And I can't switch it on for a few minutes. If I try to use the power switch, nothing happens. Then after 2-5 minutes, I can switch it on. (it then fails when I get to log-in or shortly after).

So, why the delay? Why can't I simply try to start it again? If this a clue? Does the power supply unit need time to reset? This delay maybe infers it's not a memory problem since I don't think memory needs time to "settle down".

OK swapped out the memory chips. I had 2 x 2Gb DDR2s and removed both and replaced one into slot 1. Nothing changed. The PC cut-out. So I don't think it's a memory chip.

Everything else looks OK. All fans operational.

So I have to presume it is the PSU. It's a big one (600W) but a no-name brand so I guess this has malfunctioned and now cuts out for no apparent reason.

I will get a new one tomorrow and try that.

Bought a new power supply unit (PSU) today and installed it. It worked. The PC booted and stayed on without switching off. It's been on for four hours now and it's working fine.

So, for posterity, my switch-off problem was caused by a failing PSU that supplied enough power to get my PC started but could not sustain a steady power supply. The symptoms were sudden switch off 30 seconds after switching on and then not being able to switch on for a minute or two until the PSU had reset itself.

I paid £40 for another no-brand that will, no doubt, it will fail again much sooner than it should. But I wasn't prepared to spend £80 on a good one.

Anyway, problem solved. :)

Thanks for letting us know :)
Don't skimp on a good PSU - other wise you may be back here in a few months time

Take care and regards