I've got the same problem I've read about in other threads here about the screen going black during games., but in my case it's rather wierd. My screen goes black no matter what game I am playing. Can be an old game like Condition Zero or Left4dead2. screen goes black but there is still sound, then the monitor shuts off unable to find a signal.
I have two computers with pretty much the same specs- pentium core duo 2.8 ghz, 3 gigs ram, both have Nvidea geforce 9500gt and one has XP and the other windows 7. One is an emachine and the other a Dell.
The thing that is wierd is that both PC's run games perfectly with the same gpu's in both, Nvidea 9500gt, but one gpu developed a bad fan after awhile. and so I took that 9500gt out of that one and took the other 9500gt with the good fan out of the other PC and installed it in the computer with a bigger HD. Now when playing any game it can play perfectly for a few minutes to an hour then the screen goes black and there is nothing you can do about it. ctrl\alt\dlt won't bring the screen back on to get to the task manager, and the monitor shuts off and I must do a hard shutdown at the power button and restart.
I reinstalled both the drivers that came with the gpu and updated drivers from Nvidea's website. neither works and the problem still exists. If I install the gpu with the bad fan back in the computer having the issue, the problem is resolved and if I install the cpu that I switched out back where it was originally in the original pc it works in that one as well, so placing the two gpu's back in the original pc's they were in works, so this means it's not the operating system causing the issue. it's not corrupted drivers either, not a mother board issue, or an issue with the cpu or for that matter registry issues or anything else I can think of. It's just plain weird. Makes no sense. Anyone have any idea what the hell could be going on?