My PC keeps randomly deciding it's bored of what I'm doing and turns itself off. No error messages or hanging, just working fine one instant and powered down the next. Occasionally it will boot back up and run fine (until it happens again), but usually it will either turn itself back off a few seconds after turning it on or just sit there sending nothing to the monitor and making a lot of fan noise until I leave it off for a few hours. It seems to go days or weeks without incident and then do it 3 times in one day (like today).

Running Windows 7, spec should all be in my profile (bit creaky but really should be holding up). I'm sometimes running a lot of stuff at once, but other times I'll have barely anything running when it dies so I can't imagine activity is a problem.

I would quite like this to stop happening. Please tell me if there's anything I can do to at least help diagnose what's going on (symptoms suggest maybe it's a heat problem?), finding crash reports or something.

:<

Sounds like symptoms of dying hardware, possibly PSU related but could also be something overheating.

Get speedfan and look at the temps reported in there. It should tell you if things are getting a little toasty.

Also have you looked inside recently? How many dust bunnies are there in there?

PSU would have been my guess as well.  Especially since it refuses to turn back on sometimes.

Oscar, the next time it does that and won't turn on try pulling the power cord from the wall for a few minutes and then see what happens.  Or, better yet, if your PSU has a rocker on/off switch try turning that off and back on and see what happens.  Sometimes that resets things.  But I'd still guess, from a great distance, that the PSU is dying.  Any squealing noises or anything like that coming from it?

Every time it happens I turn off the PSU power switch and unplug the cable for a bit anyway. It has actually been fairly good about restarting when I try the last few times, but I like to be safe and give it time.

Will give that a spin, cheers.

I usually pop open the case when it starts buggering up and poke at everything. Literally, I have no idea what could be wrong so I just fiddle with all the connections to make sure they're solid. I even reseated the RAM once. :-$ It is a bit dusty but not unreasonably so, I actually cleared it out quite recently.

Anyway you can borrow one to test with? I'm pretty confident that that's the issue, but with computers you never can be positive.

Can you be negative? Or maybe neutral?

Oh I can do negative very well!

It's classic overheating symptoms, which could be dying PSU (most likely), dying CPU fan, poor case ventilation generally (you've dusted it recently so unlikely) or dying CPU (never happened to me in my PC-owning life). Try running it with the side panels off. If it runs without crashes it may be treatable by cleaning &/or replacing fans. But it's your PSU.

+1

This has been happening to me too, changed the graphics card to see if that was causing it but it still happens.
Likely the same cause so I'll be keeping an eye on this thread.

Did you reply to "All"?

How did you manage that?

Took out Ken's name and typed All.

Meant to be to everyone but didn't realise All was a user.

(Opera mobile on my Android if it's not meant to be possible and needs fixing.)

You don't need to type anyone's username if it's to all, just leave it blank.

There should also be a "Reply to All" link at the bottom of the messages page, which will do it for you.