Strange Pc Occurance

ok so about a month ago i got a new vcard when my 8500gt died. the new card is a ati hd 4670, for 2 weeks it ran flawlessly without a hitch. then one day my screen blacked out and wouldnt come back on. i took the card out and reseated to no avail. did this for 2 hrs. finally gave up went to sleep. got up the next day said wth one more time. put it in and it worked no problem. so my comp ran for a bit and again same thing happened.

now im having the issue where my comp will run decently for awhile (unless i stress it with games for 6hrs), but when i shut it down, the video card doesnt wanna work for 8-10hrs after. and lately the system doesnt wanna start up until about that time as well. if i take the vcard out tho the system runs just fine, i even threw in my old card that is all fucked up and pixelated and it boots just fine and doesnt shut off. so im confused and looking for info. whats strange is after w/e time passes the comp starts up and runs fine unless i super video stress it for a bit then it'll go black screen and not work again for that time.

ive reseated all the power connections. i even took the dvdr off to see if that was using too much power or something.
reseated the ram
reseated and cleaned the card and updated the drivers.

any help is appreciated :)

Power supply.

^^^^^^ what he said, it seems your PSU doesn't have the current to run your system stably. It would be a shame to toast yet another graphics card because of an unstable PSU.

System specs would tell us more

sounds like a power supply problem or your card is overheating.

(in case the GC is over heating)Take the side panel of your pc off and put a box fan on it on high speed.


Or could be a defective Graphics card.

I've got the SAPPHIRE HD 4670 GDDR4, and on occasion It does what you said.
http://www1.sapphiretech.com/us/prod...w.php?gpid=279

But my power source Is the Corsair HX1000W, so there Is no lack of power
http://www.corsair.com/products/hx1000/default.aspx

Tho I've read that the SAPPHIRE Is a little twitchy, and I now believe they use GDDR3 Instead of the GDDR4.

I still don't know why It does It?