I am hoping you can help as you have done many times before. I built a PC for my kids last December and it has been running fine until about a month ago. Last month it started this annoying habit of shutting down by itself with no error messages and no reboot. Sometimes it would last 5 minutes, sometimes 3 hours.
Now, I thought overheating of the cpu might be the culprit and I took a look at their case...all fans appeared to be running fine however there was a lot of dust. I checked the CPU temp listed in the bios and it said 76C...my son was playing a game just before I checked so I guess that might be considered a load temp...although, I did reboot and stuff so it may have dropped some before I got to it (not sure how that works exactly...or how quickly the temp drops).
Then I did a major dust cleaning of the case, the fans, the components, the intakes, etc. When I booted it back up the temp was around 50C and then climbed up to around 60C within 2 or 3 minutes.
Any thoughts? Is the shut down related to the temps? Whether it is or isn't, are the temps still too high? What should an average no load temp be (in the 30's?)?
The HSF might need to be re-seated and have new thermal paste put on it but if I was you get rid of stock completely and buy a Xigmatek HDT-S1283 they are very good HSF and should fix your problem. However it could also be faulty ram or a overheating North Bridge. Try swaping around the ram and leaving one stick in and taking anouther out .etc & also try running memtest.
It would also be good to get some 'real' temp readings in Windows. Use a program like Speedfan to monitor temperatures at idle and at load.
76c in BIOS is way high, and after you cleaned everything, seeing it go from 50 - 60 in 2 or 3 minutes in BIOS is still a concern, in my opinion.
As fatty recommended, remove the heatsink and clean its base and the surface of the CPU heat spreader, reapply your thermal paste and reseat the heatsink. The Xiggy s1283 with its bolt through kit retention bracket is also a good recommendation. It would give you peace of mind over the stock HSF with its inadequate push pins.
1) With the PC unplugged, try to wiggle the cpu heat sink. If it is a bit loose, it is not mounted properly, and is likely part of the problem. An oem heatsink like the Xigmatek mentioned is cheap, and will do a better job.
2) Check that all fans are spinning, and in the proper direction. Dangle a piece of tissue in front of the fan to see if it sucks or blows.
3) Open up the side of the case, and direct a house fan at the innards. If the problem goes away, you have a case cooling problem.
4) The 8800GT will let lots of hot air recirculate in the case. A dual slot card will help cooling by expelling the hot vga air directly out the back. If you are inclined to upgrade, there are many options. If not, you can get an EVGA Akimbo cooler for the 8800GT: http://www.evga.com/products/moreinfo.asp?pn=202-F2-EV0...