PC Hangs when gaming

There aren't any BSOD's happening by the look of things, but I did notice a few of these errors prior to you initialiing the memory diagnostic:

Code:

Event[32667]:
  Log Name: System
  Source: Microsoft-Windows-DistributedCOM
  Date: 2014-12-05T18:10:47.000
  Event ID: 10016
  Task: N/A
  Level: Error
  Opcode: N/A
  Keyword: Classic
  User: S-1-5-18
  User Name: NT AUTHORITY\SYSTEM
  Computer: Alex-PC
  Description: 
The application-specific permission settings do not grant Local Launch permission for the COM Server application with CLSID 
{C97FCC79-E628-407D-AE68-A06AD6D8B4D1}
 and APPID 
{344ED43D-D086-4961-86A6-1106F4ACAD9B}
 to the user NT AUTHORITY\SYSTEM SID (S-1-5-18) from address LocalHost (Using LRPC). This security permission can be modified using the Component Services administrative tool.

Start with this:

1. Ensure Windows is fully updated
2. Ensure all device drivers are updated (e.g. video card, sound card etc. etc.)
3. Run an sfc/scannow to check for corrupt system files:

1. Click Start
2. In the search box, type cmd
3. In the list that appears, right-click on cmd.exe and choose Run as administrator
4. In the command window that opens, type sfc /scannow and hit enter.
5. Report the output from the command window once it finishes.

Did you check for and install any updates?

OK. You could try testing RAM again, but using the industry standard test:

RAM - Test with Memtest86+

I don't think its a RAM issue though. Possibly an overheating problem. Please follow this, and post back screencapture images of temp.:

CPU - Stress Test Using IntelBurnTest

As I mentioned before, post screencapture images of temp. and test.

OK. Run this tool for 20mins and report temperatures please.

Video Card - Stress Test with Furmark