Random Black Screen Shutdowns

I am getting totally random black screen shutdowns. I have read through a lot of the other threads and find nothing that relates to my situation. Running W7 Pro 64 bit on a home built tower PC. Not a single problem for the last 5 years. The shut down can occur after several hours or as little as ten minutes, while surfing the net or just idling. It will try to restart and sometimes it works, other times it offers me the DOS page to restart in Safe Mode etc. It even died once while in Safe Mode, and a couple of times while attempting to reboot. Sometimes it just goes into an unsuccessful reboot loop.
I have low to normal temperatures showing all the time. I have checked and reseated all connections and can't find anything amiss. I have looked at the Windows Event Viewer and there is a huge amount of stuff listed there but I have not got the tech savvy to understand any of it. I could understand maybe if I was trying to do something processor intensive at the time but this is never the case. I don't do games or video editing, etc. Any suggestions guys?

What is the make of your hard drive/s?

What are your exact CPU temperatures?

What is the make of your PSU and how old is it?

Run this and see if any HDD SMART errors show up. CrystalDiskInfo – Crystal Dew World

See if you can't run a full pass of error checking with HD Tune. HD Tune website

Hi, and thanks for responding.
My C drive is a Crucial M4 SSD and contains the OS and a few bits I couldn't divert to my
E drive which is a WD Caviar Blue containing my Documents and installed software, etc.
CPU temp is showing about 37.8C at the moment.
Power supply is a Corsair CX750W that was installed in summer 2013.
I ran the HD Tune-HD Transfer Rate (AV) 327.5 CPU usage -1.0% Health status OK, Error scan= no faulty blocks.
Crystal Disk reported Good 94% on the SSD and Good on the E Drive

If you can download and install Storage Executive look in there at your drive health as well. Crucial Storage Executive Tool | Firmware Download | Crucial.com

How did you move your documents folder and what not to drive E? Did you use a symlink?

Run Lifeguard and perform an extended test. Testing a drive for problems using Data Lifeguard Diagnostics for Windows | WD Support

This could also be a PSU issue and not even a HDD issue. The only way to be sure is to try a new PSU.

Did you install any hardware or software prior to you noticing this happening? Sometimes a rouge USB device can play havoc on a computer.

When I first set up the PC I didn't want the default Documents and its newfangled Librarys to be located alongside the OS on the SSD. I just ignored it and created a new folder on the E drive and named it Documents. Whenever I install new software instead of sending it to the default C drive address I take the option to browse and go to the E drive and create a folder there before hitting the OK button. It works fine as long as there is the option to choose the target location.

No, I didn't install any new stuff just before the problems started. This build has been amazingly stable and trouble free pretty much from day one.

I will try the tools you suggest and report back. It may be a while. I was stuck in a reboot loop yesterday for nearly an hour. I managed to get into the motherboard monitor for a look see. It was showing M/B temp as 26C and processor temp as 25C. The Asus motherboard is set to monitor and control the fan speed as necessary.

OK, here it is.
Did both sets of drive tests and luckily had no blackouts during either. With the WD tool I got Successful with quick and extended tests on both drives. With the Crucial test on the SSD it reported Good Health. In the details list I spotted "6% lifetime used" and "321 unexpected power loss events". That's all for the moment. Do you think I should do a similar test run on the memory? Meanwhile, I might have to see if throwing money at a new power supply will do the trick.

You can test your memory with Memtest 86. Use a CD or USB stick and boot Memtest 86 like you would to install an OS. There are like 11 or so tests in Memtest's options. I'd chose them all. Hopefully the computer doesn't black out during RAM testing.
MemTest86 - Official Site of the x86 Memory Testing Tool

Do you have the latest BIOS by chance? I'd be weary about updating it right now though. If your computer powers off during the flash and if you don't have dual BIOS your MOBO is effectively dead.

The PSU could be the issue here. It's really hard to determine unless you use a process of elimination. Since this problem happens in safe mode as well, it would seem to me the problem is hardware related.

Hi again. I'm one step ahead with that idea. I read that Memtest 86 was a respected tool so went to their site and downloaded it. I have it on a USB stick now but in my M/B bios there seems to be no option to have a USB as the first boot device. Is there any other memory test that can be done without booting into it?

Oh, and Happy New Year!

According to the manual of your motherboard, you should be able to pick a boot device by pressing F8 at the ASUS logo on boot up. You may have to do this really quick. Your motherboard certainly supports booting from USB.

I'd rather see you use Memtest 86, but Windows its self has their own RAM testing program built in. Go to Search and enter, Windows Memory Diagnostic.

Aardvarkly said:

Oh, and Happy New Year!

Just another solitary day for me.