How hot is too hot? (Or, how my graphics card burned my fingers)

Note: I originally set setup logo, I meant startup logo. This system has had Windows installed for awhile now.

I installed a new Core 2 Quad in my system and was getting ready to do burn-in testing, but the thing froze during the Windows startup logo. Naturally, I thought it was something I did, so I re-checked to be sure the processor was seated correctly and the RAM was all seated properly.

Finding nothing wrong, I booted it back up and instead of being greeted by the usual login screen, I was staring at a 640x480 login screen! Odd, I thought. So I logged in and the ATI driver complained about how I either didn't have an ATI graphics card installed or the driver needed updating. Device Manager reported a generic VGA Adapter. So I shut it down and went to reseat the card. I found the heatsink was so hot it burned my fingers!

Of course, reseating it didn't do a thing, so I reinstalled the driver, got my usual resolution back but found it was idling at 79° C! Of course, it keeps randomly freezing during start up. The processor is nice and cool at 38° C, so no issue there. Is the graphics card toast? The graphics card in question is an ATI Radeon HD 4850.

Update: I'm running four instances of Prime95 and an instance of ATITool testing for artifacts overnight. Hopefully this will help narrow down the issue.

Testing results after 13 hours of ATITool and Prime95 show that the processor never exceeded 65° C and the GPU hovered around 89° C with no artifacts. I swapped the old processor back in and the freezing during startup persists. I was able to figure out that if the system is completely cooled and I boot it, the problem will reliably occur. For now, I've swapped in an 8800 GT to confirm that it is the graphics card.

you will need to RE APPLY your thermal paste to the GPU... it will fix your issue and your grafics card will last longer. If you wanted you might want to think about underclocking the gpu or maybe changing its voltage core.

Unless your new CPU is a significantly higher TDP model and your case is poorly ventilated I think the timing issue with the upgrade is coincidental. I suggest removing the card from your case, immobilizing the fan (some fans can be damaged if overspun) either with your finger or by sticking something inside and blasting it with canned air to clean any dust out.

The ATI 4800 series of GPUs are notoriously hot, and the reason is that the auto fan control defaults to keeping the system quiet rather than keeping the GPU cool, so they tend to idle around 75ish. If you install the latest drivers from ATI.com with the catalyst control center you can manage the fan speed manually. I have my 4870 set to a standard 40% fan speed with no issues at all and it never gets above 65C, even under extended load.

Well, the problem ended up being the motherboard. After spending an hour on the phone with ASUS, they insisted that it was everything but the board. They finally settled on the power supply, insisting that it was insufficient, even after I pointed out that it ran fine for two years. I verified my hunch by putting in a Gigabyte GA-EP45-UD3P (well, actually two, the first one had defective LAN ports) and it works perfectly fine.

The power supply, an Antec Earthwatts 380 watt unit is plenty for my needs, according to http://extreme.outervision.com/psucalculatorlite.jsp and it never once hiccuped while the system was under stress from four instances of Prime95 and ATITool's artifact finder. They absolutely refused to acknowledge that there might be a short in the board due to the issue only happening when it is cold. After that kind of rude behavior, I will never recommend them again.

Thanks for everyone's help!

although the card can easily cope with temperatures beyond 100c, 79c idle is too high, should be 50-60c.

did you install the chipset driver for your mainboard? check the video card manufacturer's website for a BIOS update. also, the card manufacturer may offer different drivers to the generic ATI driver.