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I have a weird problem that has me baffled. A few days ago, my wife reported that, when she went to run a program for our daughter on an alternate login, my machine was "off." I asked her if she wiggled the mouse, would it come back "on." And she said no. She reported that the fans were still running, but the OS was not responding, and not even on. The monitors were on but had no signal.

I went into Windows logs and found some relatively worthless message saying "the last shutdown was unexpected." This is because I had my wife reset the machine to get it started again. After a reset, she reported that it worked as normal.

I got home today and the same thing was happening again... No OS, but running fans, CPU fans, power source fans, but no OS. I took the covers off and cleaned the guts and aired out the components. I inspected it and no obstruction seemed to be apparent (I thought maybe the system was overheating or something due to a wire interfering a fan...).

So I'm not sure what's going on. No real updates or new software in the last few days to have caused this. I'm thinking maybe some kind of tool that will monitor my system and report to me any failures? Does anyone know if any way to troubleshoot this?

Any ideas are appreciated.

EDIT

Ran chkdsk and turned up no bad sectors. HDD seems to be good. Off to do a memory test now...

EDIT 2

Memory test yielded no problems, so I'm assuming the memory is good.

EDIT 3

The good news is that overnight the machine is still running fine, EXCEPT:

I went to connect to the network and my network adapter was gone. I mean completely missing, no device at all. Troubleshooting revealed I needed to install a network adapter and its driver. I rebooted and all is well. Not sure if this is related but it sure is odd...

EDIT 4 Seems to be running OK all day. I have on-board video, so I will need to look into testing an external card for the next phase of testing. Thanks for all the good ideas so far.

FINAL EDIT

I think the manual cleaning/air-out/inspection helped. Maybe my connections were loose and I snugged them in when I had the box open... I opened the box again, and just made sure everything was in its place, and I haven't had problems in two days.

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I think you might want to test with another video card if possible. Also, if feasible, see if the machine responds to ping requests and / or a remote desktop connection when it happens again. This will help narrow down the issue. –  user3463 Apr 27 '12 at 3:46
    
That is a good idea - thanks for that... –  nicorellius Apr 27 '12 at 15:12
    
I think Randolph is on to something with the testing another video card idea because to me it sounds like your video card is starting to fail. –  djmadscribbler Apr 27 '12 at 16:30
    
If your NIC is disappearing, that could be a) corruption due to forced reboot, or b) [more likely] motherboard beginning to fail, which would account for the other problem you're having with video. How old is the machine? –  user3463 Apr 27 '12 at 18:10
    
The machine is not too old. In fact, the motherboard, RAM and CPU are about 1.25 years old. I'm not saying it's not the motherboard, but that would be a shame. I have a few good ideas from this post, however, so I should be able to get somewhere. Thanks. –  nicorellius Apr 28 '12 at 0:14
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3 Answers

Check your settings - do you have the system set to turn off the video or to go to sleep? If so, try and disable them. Sounds like the system is still up, but not outputting a signal. For Windows 7, right click a clear area of the background, select Personalize, choose Screen Saver and then set it to none. Under Power management, go into your current power plan, change the plan settings and make sure your video is not set to turn off the display and not sleep. Test that for a day or two.

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These were the first things I tested... –  nicorellius Apr 27 '12 at 15:11
    
I double checked anyway, and these display/sleep/screen saver settings are the same ones I've had for quite some time... –  nicorellius Apr 27 '12 at 15:18
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Test with your keyboard: Try pressing NumLk (or another Lock key), and see if the light updates. If not, the system is messed up. If it does respond, then I would look into the video card/plug/cable or the monitor.

If the light does not change on your keyboard, I would be checking the Applications log as well, and scan for viruses/malware.

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Thanks for the comments. Already looked through the logs; nothing valuable. –  nicorellius Apr 28 '12 at 17:18
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After this started happening again, I took another look. I started to suspect my hard drive. So I bought another drive, put it in the same machine and installed Ubuntu on it. I started to do a backup of the data on the suspect drive and after the *.tar.gz I was creating to back these data up got to around 12 GB, the computer just shutdown.

I started it up again and repeated the compression and it happened again, same spot, right around 12 GB. This indicates that the drive has some bad data on it at that point, and in the past when I've encountered these data on a backup or under load, it crashes.

The solution is to reinstall Windows, and slowly transfer data over to new drive. Or just leave the old drive in there and access data as normal. THe only real bummer is that I can't back these data up all at once.

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