Help needed diagnosing random shutdowns

[xboxist]

System in signature has begun shutting down randomly on me. Five times in the past two days. I can't correlate any sort of trigger to the behavior. I was playing Portal once. Web browsing a few of the times.

I will be doing normal activities, and then out of nowhere - without any sort of warning/errors - all programs/windows will begin to close and then the "Windows is shutting down" message. It acts EXACTLY as if I were to command it to shutdown through Windows.

In my limited knowledge of computer troubleshooting, my first thought was overheating somewhere. I downloaded the latest SpeedFan and I don't see anything unusual. CPU/GPU read anywhere from 35-45C.

Although I build my own computers every five years or so, I'm not the sort of user who has all sort of spare parts or extra machines laying around to do swaps with, so this is making me really nervous. Not sure where to begin.

 

[Jaydip]

Did you check for virus/malware?

 

[xboxist]

I have Malwarebytes and MSE - nothing found. Should I scan with something else?

 

[Bubbaleone]

I'd suggest you go to Control Panel and click on Power Options, tic "Balanced (recommended)", click on "Change plan settings", then click on "Restore default settings for this plan". This is the default power plan for Windows and will give you a known starting point to begin diagnosis from. Carefully observe your PC for any changes in behavior after doing this, then post back with the outcome.

.

 

[paul878]

That's usually power supply problem or bad Capacitors on the motherboard.

 

[monkeydelmagico]

That's usually power supply problem or bad Capacitors on the motherboard.

Faulty power supply or bad caps isn't going display "windows shutting down" splash prior to pulling the plug. This is more likely to be a software based problem.

Check logs for updates requiring restart.

 

[xboxist]

I'd suggest you go to Control Panel and click on Power Options, tic "Balanced (recommended)", click on "Change plan settings", then click on "Restore default settings for this plan". This is the default power plan for Windows and will give you a known starting point to begin diagnosis from. Carefully observe your PC for any changes in behavior after doing this, then post back with the outcome.

.

Ok, done. It was already on balanced, but I did a settings restore anyway. Thank you for the advice.

 

[xboxist]

Check logs for updates requiring restart.

Are you willing to elaborate on where/what to look for when doing this? Thank you.

 

[monkeydelmagico]

http://support.microsoft.com/kb/902093

Seems like something may be doing updates without your consent/knowledge. By checking this log you can see if it corresponds to dates/times that you've had random shutdowns.

 

[xboxist]

^

Wouldn't Windows Updates result in computer restarts, and not shutdowns? I will check that out.

 

[Ketchup]

Do you run a battery backup?

 

[xboxist]

Do you run a battery backup?

I don't.