Radeon HD 5670 turns Black screen when gaming

So I play Starcraft 2 and Diablo 3, the desktop is stock from Dell with ATI Radeon HD 5670 1GB video card. It plays fine for 2 hrs or so then the screen would freeze for about 3 seconds and then the screen goes black for 10 to 15 second. Sometimes the game recovers sometimes the PC would crash. Please help me out, FYI I am a computer newbie. Below are my set up. Thanks.

Dell Studio XPS 8100 Window 7 Home Premium 64Bit

Processor:
Intel® Core™ i7-870 processor(8MB Cache, 2.93GHz)
Memory:
6GB Dual Channel DDR3 SDRAM at 1333MHz - 4 DIMMs
Hard Drive:
750GB - 7200RPM, SATA 3.0Gb/s, 16MB Cache
Video Card:
ATI Radeon HD 5670 1GB GDDR5

Maybe I should upgrade my driver?
Maybe I should get MSCI Afterburner to overclock it?

MSI Afterburner has known problems with Windows 7 and is not recommended. Overclocking is very much not recommended if you already have stability issues. Your crashes indicate a TDR soft error. A hard error will result in a TDR error that blue screen crashes. Either way, you should troubleshoot the same way.

• If you are overclocking any hardware, please stop.
  
  
• 
  
  H2SO4 said:

  These are all stop 0x116 VIDEO_TDR_FAILURE conditions.
  
  It's not a true crash, in the sense that the bluescreen was initiated only because the combination of video driver and video hardware was being unresponsive, and not because of any synchronous processing exception.
  
  Since Vista, the "Timeout Detection and Recovery" (TDR) components of the OS video subsystem have been capable of doing some truly impressive things to try to recover from issues which would have caused earlier OSs like XP to crash. As a last resort, the TDR subsystem sends the video driver a "please restart yourself now!" command and waits a few seconds. If there's no response, the OS concludes that the video driver/hardware combo has truly collapsed in a heap, and it fires off that stop 0x116 BSOD.
  
  If playing with video driver versions hasn't helped, make sure the box is not overheating. Try removing a side panel and aiming a big mains fan straight at the motherboard and GPU. Run it like that for a few hours or days - long enough to ascertain whether cooler temperatures make a difference. If so, it might be as simple as dust buildup and subsequently inadequate cooling.
  The above quote was taken from https://www.sevenforums.com/crashes-d...tml#post280172, which is linked to in usasma's thread about this error. Closely follow the first three posts of usasma's thread outlining STOP 0x116: VIDEO_TDR_ERROR troubleshooting and proceed through each step. Let us know if you need further help.

Also, please follow the https://www.sevenforums.com/crashes-d...tructions.html even though you are not having a blue screen crash. The logs they provide can help with system and application errors in addition to blue screen crashes.

Prissy said:

Maybe I should upgrade my driver?
Maybe I should get MSCI Afterburner to overclock it?

You are already having problems and to overclock would add MANY more. what are you after? Stability, or OC'ing?

Stay focused and let Writhziden walk you through the problem.