Hi there, I've been having a little problem with my computer since I added some parts to it last week.
Prior to building it, I used a dual-core intel cpu (2.66 GHz), a EVGA NVIDIA GTX 280 video card (x1), an XFX nforce 680i LT SLI Motherboard, 4 gigs of DDR2 RAM, a 750watt power supply by Apevia (I think that's the wattage, I'm not sure since there's no stickers or anything on it. I know its either 750w or 850w). It looks exactly like..http://www.directron.com/atxlcd750w.html. All of this was inside of a midsized case by Apevia. Case (http://www.apevia.com/ProductsInfo.asp?KEY=ATXA8NW-BK/5...)
Now last week I upgraded my motherboard to a P7P55D PRO by ASUS, 8 gigs of Corsair DDR3 RAM, and the CPU to an i5 running at 2.66 GHz (no overclock yet.) All of my heatsinks are stock, as well as the thermal paste on the CPU.
Now for the problem: I'm kind of an avid gamer, and since building this, I have tried several games including Borderlands, Torchlight, Dragon Age: Origins, Left for Dead 1 and 2, Team Fortress 2, and Grand Theft Auto IV. When I play GTA IV, my computer will after a random amount of time, usually 5-15 mins (sometimes less) randomly shut down the entire system. When it shuts down, there is no BSOD, and no error message besides the normal "your computer was not shut down correctly" crap with options to start in safe mode. Initially I figured this was a heating problem. To attempt to solve it for a little while before I bought anything like heatsinks for my GPU/CPU, I put a medium sized desk fan on it with the side of the case removed. As expected, this reduced the temp of most of my parts by a few degrees celcius. So once again, I booted up the game....and it crashed my system.
I then downloaded the EVGA Precision Utility that allows you to change settings in your GPU, and set the fan to 100% manually. Booted GTA up...and it crashed, although I should mention it has been working for a little longer time after doing this.
After that, I downloaded SpeedFan to check out my system temps, to see if something is heating up way too high while playing the game.
From this I could see nothing really out of the ordinary, although I'm still not sure why my 3rd core always runs hotter than the others, especially while I'm gaming.
When I'm playing GTA IV:
GPU: Anywhere from 54-72C depending on how long I play.
System: 54-60C tends to be about the norm.
Now, from looking at those numbers, nothing looks too out of whack. Nothing is overly hot, so at this point (unless someone tells me differently) I don't think I need aftermarket heatsinks. Also, if I alt tab out of the game, all of my parts immediately cool down by large amounts while I'm not in the game. Doing this allows me to play for much longer periods of time as long as I alt tab every couple minutes (which as you can imagine, is annoying as hell.) This continues to allude me, and make me think its a heating issue, but I'm not sure whatsoever.