Hard Crash during game play only.

Hello,

I have a recurring problem. While playing several games, Half-life 2: Episode One and Two as well as Portal, I am getting intermittent and unpredictable crashes. This does not occur at anytime other than during game play.

Specifically, what I mean by crashes are an instant shutdown. There is no warning, no stuttering or artifact on screen. Before I can restart, I have to cycle the power button on the PSU.

I have put about 8 hours into solving this myself with limited success.

My system is as follows:
GIGABYTE GA-770TA-UD3. // OCZ Fatal1ty 550W // AthlonII X3 440 3.0GHz. // POWERCOLOR Radeon HD5770. // Crucial Ballistix 4GB DDR3 1600. // SAMSUNG Spinpoint-F3 500GB 7200RPM // Win7 Home64.

All are running at stock speeds. My GPU stays below 65 C. My CPU stays below 52 C. I have good airflow through the case.

When the crashes occur, there is no obvious loss of power to any other device in the house. No flickering lights etc. Also, I live in a newer house, under 10 years old, so presumably wiring would not be an issue.

I discovered that Windows Security essentials was the cause of some of the crashes by referring to the event viewer.

Session "Microsoft Security Essentials OOBE" stopped due to the following error: 0xC000000D

So I removed and reinstalled, it stopped for a couple days, then started, so I deleted the specific file as noted in these forums elsewhere. This resolved it again for a day. I finally removed the entire program. However, the crash JUST occurred again.

I checked the Event Viewer and All I could find were:

"The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly."

"The previous system shutdown at 5:43:01 PM on ‎12/‎8/‎2010 was unexpected."

I have also done the following:

-Scanned the entire system with Windows security essentials and Malawarebytes.

-Defragged the HDD.

-Verified that the start-up processes are legitimate.

-Disabled Windows Defender.

-Verified the Files in my Steam directory.

-Updated the GPU Driver.

-Verified that my router has the latest firmware.

-Verified that windows is up to date.

-And ran MemTest86 as well as Windows Memtest.



Is there anyway to identify what is causing the crashes? I have reached the end of my diagnostic abilities. I am hoping that I can avoid the final option of the fresh install.

Please help!!!

Thanks : )