I recently upgraded my GPU to a GTX GeForce 780 but on high graphic games it randomly crashes after a few minutes.  There is no hanging or error message, it is as if the power was cut for a second.  Windows logs this as an abnormal shutdown.  I have RMA'd once and it still happens so I do not think it is the card.  I have tried using Precision X to reduce the target power to 90% but it made no difference.  I have tried a couple of different NVidia drivers but it has not made any difference.   I have not changed any of the factory settings or switches.  I've used Precision X to log temperatures and voltages and they all appear stable up the crash point.
 
Low intensity apps like Firefox cause no problems
 
My system is:
Intel Core 2 Extreme CPU X9650 @ 3.00GHz 4 cores
Bios American Megatrends Inc 1001
OS Windows Vista 32 bit home basic SP2 build 6002
Memory 4GB
GPU EVGA GeForce GTX 780 Dual Class
Display 1: Dell 2408WFP
Display 2: ViewSonic VP 191s
Driver NVidia 337.88
Power EZCool 600W
 
The only thing I can think of is that the power needs boosting
 
All suggestions welcome.

Welcome to the forums..I would suspect that cheap PSU..Personally, I would just go buy a reputable name brand unit such as Corsair, EVGA or Seasonic with at least 700W and a single +12V rail, install it and go from there..There are other  suitable quality units, those are just my personal preferences.
 
You can get a good idea of your overall system power requirement using this PSU calculator..The GTX 780 is a 250W card.

Thanks very much, The kit was last upgraded six years ago, I was trying to avoid spending ages mucking around with CPUs and motherboards, I will upgrade the SPU, (getting the current SPU to the GPU took quite a lot of splitters and extra connectors).

KellerKind
sorry ^ 

Thank you. It would probably be best if you're needing to troubleshoot an issue you're having to start your own thread and list all your hardware specs. Motherboard, processor, memory, PSU, any overclocks, Operating System etc etc... The more detail, the better including what issues you're having and under what conditions.

KellerKind
thank you for the suggestion but ^i thing my problem is the windows , cause with the windows 7 , i did not have any crashes or raindom restarts  >.>

The OS doesn't usually cause crashing in games unless there is some other issue going on. I've been running Win 8.1 for quite some time and I've never had a game crash due to the OS.