System shuts down every hour-not a blue screen issue

I am new to Sevenforums and I can not find a thread with recent posts concerning my issue. Pleae guide me to where I should post to receive help/input.
My situation:
System worked perfectly for about a year after build in early 2012; after a few weeks of not being used due to my absence while traveling/vacationing, I returned to find that the system shuts down again and again at intervals of 63 minutes after booting up. I have searched all leads that I can find via the internet but nothing that fits my situation. I have used Aida64 Diagnostic tools to check the temperature and no issues found; I have done 2 restores>no success. Event log does not explain... but then I am a novice and may very well be missing some clue that is there.

Thanks TVeblen for the suggestion; I checked every line item within the Task Scheduler but found nothing of help. I did disable a few routine tasks (such as Google) that showed a frequency of one hour but no luck in addressing the issue. I have no idea of where to go next in finding a solution.

Establish a Clean Boot as shown in Troubleshooting Steps for Windows 7 to see if prob persists.

If not work through the other steps to go over your PC thoroughly.

If nothing comes up pursuiing software and hardware then I'd get a perfect baseline Clean Reinstall - Factory OEM Windows 7 (same for retail) after wiping the HD of all boot code with Diskpart Clean Command. This will eliminate software and shift focus firmly on hardware.

yup, that's a pretty thorough step through, should see you right

Thanks everyone for the additional inputs.
Update from my end includes the following:
-All of the shutdowns were forced shutdowns...not managed (i.e. not as you would expect from a task command)
- the system will always start up fine when I select "normal windows start"
- I did 2 complete "clean installs" of win7; but no change in the behavior after the following boot ups
- one change after the clean installs, is the appearance of a blue screen error message showing a stop and related code
- I contacted intel online chat and their conclusion was that the problem was incompatibility of CPU with the installed MBD....a mistake had been made when the components were purchased...and that my only course of action is to purchase a new CPU that is compatible with my board or vice versa >> on the basis of comparitive costs, they recommended new board
- since my case is form factor mini-itx, there is only one compatible board for my i5-2400 CPU and that is a DH77DF.
- my requirements focus on dependability/stability; I do no gaming on this machine; we use other computers for email, browsing, media handling etc. This system is installed on our sailboat to handle multiple apps providing navigational charting, radar, ship identification systems, depth/wind/weather/etc instrumentation and integration. It is a critical system for sailing the vessel around the world which is what we have been doing; the spec and component selection was developed by an IT expert (also a sailor) last year and I, being a novice, just ordered the components and built the machine
- it worked flawlessly against its intended purpose/requirements for about a year and then this recent ongoing regular crash history
- I seem to have no way to diagnostically prove that the incomatibility is the cause...but it is the suspicion of the intel agents
- they did supply an intel CPU diagnostic tool to make sure no damage had been done to date to the CPU as a result of the incompatibility....the TEST showed all is fine with the CPU

I WOULD VERY MUCH VALUE ANY ADDITIONAL INPUT FROM SEVENFORUMS members....if nothing new emerges, I will proceed to source the new board (I guess I should say source 2 boards as, for redundency in this application, I sourced 2 of every component when I built the system last year and so I will be tossing 2 of the exisitng boards....the installed and my spare.)
THANKS AGAIN FOR INPUTS>>>>MOST APPRECIATED!!

Reply to TVeblen:
-The disc was set to 20 minutes; I changed it to zero/never...I am not expecting any change in system but we will see.
-I have no source for borrowing a larger power supply in my remote location in Malaysia....and the installed power supply is supposed to be totally adequate for the system requirements; my primary constraint is the form factor of the case as I have a location for the box that can NOT house a tower>>>therefore the choice of ITX for case and components
-Please do send me the test that you suggest regarding power supply; I do have top end Fluke multimeters so should be able to carry out whatever you suggest.
- in case it is useful in some way, here are the blue screen stop/error screen messages referenced by me in my last post:
:Ø STOP: 0x000000F4 (0x0000000000000003,0xFFFFFA8007CE2290,0xFFFFFA8007CE2570,0xFFFFF80002380350)
Ø STOP: 0x000000F4 (0x0000000000000003,0xFFFFFA8008B59B30,0xFFFFFA8008B59E10,0xFFFFF800029E3DB0)
- Thanks.

I thought I should also add these event viewer errors that keeps populating after EVERY shutdown when the system is restarting:

Log Name: Administrative
Source: WMI
Event ID 10
Words are: Event filter with query “SELECT*From_InstanceModification Event WITHIN 60 WHERE Target Instance ISA “Win32_Processor” AND TargetInstance.LoadPercentage > 99” could not be reactivated in namespace “//./root/CIMV2” because of error 0x80041003. Events cannot be delivered through this filter until the problem is corrected.

Also there is always the following event when restarting: ( Note I would expect this event since the shut down was not "Clean" in each case)
Log Name: SYstem
Source: Kernel-Power
Event ID: 41
Level: critical
User: System
Words are: The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.