Shutting Down Unexpectedly

I am from Dell Social Media and Community.

There could be several reasons for system to shutdown while using the system.

First I would recommend you to run a basic hardware diagnostic test from the following link to confirm there is no hardware failure.

http://supportapj.dell.com/support/topics/global.aspx/support/kcs/document?docid=DSN_300428&isLegacy=true

Check if your system has any overheating issue.

Or

Steps Recommended by Microsoft team.

Method 1:
Boot the computer in safe mode and check if the issue still persists
i. Restart the computer
ii. Start tapping F8 key
iii. You will get advanced boot option window
iv. Using the arrow key select the option “Safe mode”
Link: http://windows.microsoft.com/en-US/windows-vista/Start-your-computer-in-safe-mode

Method 2:
If the issue does not persist then boot the computer in clean boot to check which third party is causing the problem. To help troubleshoot error messages and other issues, you can start Windows 7 by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.

Follow the Steps listed below in the link to perform clean boot and check if you have the issue. If the issue is resolved check which third party is causing the problem.


Reset the computer to start as usual
After you have finished troubleshooting, follow these steps to reset the computer to start as usual:
i. Click Start, type msconfig.exe in the Start Search box, and then press ENTER.
ii. If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
iii. On the General tab, click the Normal Startup option, and then click OK.
iv. When you are prompted to restart the computer, click Restart.

Method 3:
Unplug all external devices and check if that helps. Follow the steps to do the same:
Go to device manager and disable
i. Sound card
ii. Video card
iii. Network card
iv. Modems
v. Ports (serial and parallel)
And then restart the computer and check. If the issue still persist.

Method 4:
Update all the drivers installed from device manager. Steps to follow
i. Click Start, type devmgmt.msc and press enter.
ii. Expand the driver you want to update and right click on the sub item and click update driver.

Dell-Niranjan