Windows 7 Premium Dell computer random shutdown troubleshooting

I am working with a friend whose Dell small form factor desktop computer (OptiPlex 3010, Core i5) running Windows 7 Premium randomly shuts down almost exclusively at night when it is not even being accessed by anyone. I suspect it could be because of heat since the AC is turned off at night in this small office building.
I am in the process of collecting its configuration details so for now, information is sketchy. There is a UPS feeding power to this computer. When it shuts down, it does not reboot by itself. I have looked at the EventViewer logs and do not see any major (red) events. The computer is being used as a 'server', primarily to serve network storage for sharing files with his 3 office computers.
With this limited information, I am asking if there is a sticky troubleshooting guide to systematically test and identify the root cause of this issue to bring some reliability to his little 'server'.
If it is determined to be because of heat, what can be done other than keeping the AC on all night?
Thank you.

Hi rmk9785e, Welcome to Sevenforums.

Try this,

1. Click Start.
2. Type Power Options in Start Search.
3. Click on Change Plan Settings next the power plan.
4. Click the drop down and select Never for the option “Put the computer to sleep”.
5. Now check if the issue still persists or not.
6. Also check the settings by clicking on “Change Advanced Power Settings”.
7. Expand Sleep under Power Options window.
8. Set all the options under sleep to Never and check.
I also suggest that you check if any key on the keyboard is assigned to go to sleep when pressed on it.
If the issue still persists, then you may try disabling the sleep option from BIOS (Basic Input Output System), for this you may need to contact the computer manufacturer for further assistance.

Heat is a likely culprit. The small form systems are very compact and thus does not have the air flow of a full size case PC. Locating the PC where it can get as much ambient air flow around it as possible is the first step. I've seen a lot of these installed where air flow is limited.

Intel CPU's have thermal protection and if it gets too hot they will power off. The power supply is another item that can have thermal protection and if it powers off there may not be any Windows logs for that.

There is documentation on this model available at the www.support.dell.com site. Use the service tag number of the unit to access, that gets you directly to the specific model. Dell also has a support forum http://en.community.dell.com/

Check for dust in the case, also event viewer would not state anything about temperature.