Windows 7 system shuts down by itself

[llchase36]

Since I purchased this Dell Inspiron desktop in November '14, the computer has occasionally shut itself down. It has been occurring more often lately, sometimes shortly after turning on, sometimes after much longer. Fortunately I haven't lost any data. When it occurs, I reboot and select the option of "start Windows normally" and everything is fine (until it happens again .
Any help will be greatly appreciated.

 

[llchase36]

To clarify: the computer literally turns off (no power). Thanks

 

[AddRAM]

Maybe a bad power supply.

Your computer is still under warranty, call Dell for a new Power Supply

 

[llchase36]

Thanks, I will check that out.

 

[llchase36]

I am continuing to have this problem, almost on a daily basis now. However, I'm beginning to think it's not the power supply since it happens only when I'm NOT using the computer. This makes me think there might be something going on between the monitor and Windows 7. In other words, if the screen saver is on, it sometimes happens, but if I turn the monitor off (or I'm using the computer) it has NEVER happened. Would the monitor's sleep mode be involved? Has anyone ever experienced this? The monitor is an HP 20", purchased with the Dell desktop Inspiron 3847.

 

[Boozad]

Check in Event Log to see if anything is showing. Also change your Power Options to disable the screensaver and sleep options to see if the problems persists.

 

[gregrocker]

Have you run Dell Hardware Diagnostics from F12 Menu?

Work through Troubleshooting Steps for Windows 7 starting with the hardware tests, in particular check for overheating in Step 4 by installing CoreTemp to monitor temps and if necessary clean out dust.

The step for resolving repeat errors will show you how to check for clues as to the cause at the time of shutdown, per Gavin's excellent suggestion above.