weird problem.     PC  works fine.   but when i try to play any game it black or green screens and hangs til i hard reset.
 
cpu 920 i7
psu enermax 720
motherboard g1 assassin
evga gtx 570 hd
3 2terabite hd
256 gb ssd boot drive
2 dual burners.
 
tried switching pci slots,  changing power plugs to gpu and underclocking the gpu but somethings settings don't stay and don't always work.   not sure if its bad gpu or maybe faulty psu not supplying enough clean power. 
 
any help would be appreciated.  
 
 

i'm running 290.53  latest drivers

haven't tried that yet but previous 460 gt worked flawlessly.  I'll try different pc if i can.  just suprises me that it will work great with say Bastion but crash as soon as i try fallout 3 or battlefield 3.  it will actually start and i can see the game look amazing but then green screen til i hard reset.

Wow half my message disappeared what I was trying to say was replace the psu with a more powerful one you have a lot of hardware not even including your fans and everything else not mentioned your psu could be dying I love enermax but they tend to have issues after a while but I personally think it is the psu so try a more powerful one if thats not it return the psu

Yeah more than likely this is not a driver problem. A 720W power supply is more than enough to power your rig but it should be noted that some brands are more reliable than others. However it should be noted that Enermax is a solid brand the one you have got an amazing review. Also consider how old it is since the capacitors age and reduce it's max capacity over time. What you're experiencing sounds like the power supply cant deliver enough juice when a heavy load is placed on your graphics card resulting in the crash.
 
To rule out the graphics card as an issue I would put it in another computer (with a known good power supply) and see if it works.