You're overlooking on obvious culprit... your power supply. A computer under a light load (browsing the web, typing a paper, etc) does not consume NEARLY its peak power. When gaming? Yeah, that's about as close to max load as most people push their computers (for this discussion, let's ignore people who stress test their computers) So you fire up a game, your PSU heats up (because it's required to produce more power) and at some point it fails... at this point your PC probably freezes and you have to power it off and back on.
If you're worried about your memory, download and burn an ISO of MemTest86+ and that'll clear up any concerns you have about your memory. If you're ONLY experiencing this problem when gaming... well, it's very possibly a bad PSU.
Obviously your PSU was fine for many years, but it could have developed a problem... just humor me and post the specs on your PSU. There should be a label on your PSU listing various amperage ratings. Specifically, I'd like to know the +12 volt rating.
Thanks for getting back to me, will add the PSU details. But, (I could very well be wrong) it doesn't seem like a PSU fail as all I loose is the picture input, the screen will go blank and then finally enter into sleep mode. When I turn the monitor off and on again it is not receiving a signal.
But the sound of the PC, fans running etc still remains exactly the same. I just loose video signal....
Details of the PSU, from speedfan:
+3v - 3.31V
+5V - 4.87V
+12V - -11.8V
-12V - ranging from -3v to -7.9V
Is that the info you were after?
These readings were taken without a game open.
It normally takes about 10 minutes from opening a game to the screen going blank.
Take the side of your case off and check to make sure your fans are all running. I might also suggest taking out the card and using a can of compressed air to remove any dust buildup from inside the video card itself.
If it isn't the video card the most likely culprit is the power supply like rodney_ws suggested.
What brand is that power supply btw? If it's a generic Dell power supply or the like I would suggest replacing that first.
If it will re-boot when not playing a game it is probably not a graphics card problem. Besides replaces the psu, have you ran anti-virus scans and cleaned up all the temp/junk files? I would recommend backing up all your data to a drive and then re-install Windows. After Windows is used every day for 2 years, strange errors and problems start to occur to the OS. I have found that it is good preventive maintenance and fixes lots of problems to complete a clean install of Windows after about 2 years of use.
It is on a fresh install of windows on a new HDD. It only re-boots if I do nothing after the screen goes blank whilst playing a game.
I never get problems when just emailing, or on the web etc. It is only when playing games.
The computer will work fine for a while, norm 10 minutes or so, and then the screen goes blank, BUT, I can still hear the game continuing I just can't see anything. If I do nothing at that point, then after a few minutes the computer will re-boot. It is not possible to quit the game the only available manual process is to re-boot. Turning the screen on and off doesn't work.
Is your computer dusty inside? Take it outside and blow the crap out of it with an air compressor. My sisters computer literally shut off one day and wouldn't come back. She dropped it off at my parents and I used their air compressor to clean it out. I swear 4 rabbits fell out of the thing. After that, no issues. Heat is your enemy and dust gives your components a nice warm fuzzy coat.
Just a thought. Sounds like older components. She has an AMD 3200+ Athlon XP.
Also, the components in a PSU degrade over time, especially when you are straining them. It could also be your PSU is at the end of its day.
Just some friendly advice to the OP... feel free to look at the system specs of the regulars here... just click "more info / member configuration" beneath their picture and check out the PSUs these people run.
I doubt very many of us have tons of money to burn... and yet, most of the regulars here seem to go with some quality, brand-name PSUs. We do it for a reason. It's not like we saying "Do as we say" ... we're saying "Do as we do" I had problems with a PSU many, many years ago and have gone the brand-name route ever since. I may post a question or a problem from time to time here, but I'll be damned if it's about my Corsair 650 HX.
Good luck but if I were you I would ditch the generic psu and maybe replace the card with something better like a cheap 4650. If the cpu is an AM2 then it should be good enough but again the psu may be junk.