Last night while trying to download the latest update for DirectX, my computer just shut down cold. I rebooted, and in less than a minute, same thing, shuts right down with no warning. I waited about 10 minutes and rebooted again. It went a few minutes longer before it completely shut down again. My box is just over a year old. I'm thinking ... Power supply. What do you guys think?

Can you get into BIOS and let it sit in there for a while?What PSU do you have?

Ryan's suggestion is good. In fact very good :) because you bypass the operating system and DirectX that way.I'd test it that way before I made any conclusions. I just had a 10-year old PC Power power supply go out on me, so that is a possibility, but test first.RhettFS box: E8500 (@ 3.80 ghz), AC Freezer 7 Pro, ASUS P5E3 Premium, BFG 8800GTX 756 (nVidia 169 WHQL), 4gb DDR3 1600 Patriot Cas7 7-7-7-20 (2T), PC Power 750, WD 150gb 10000rpm Raptor, Seagate 500gb, Silverstone TJ09 case, Vista Ultimate 64ASX Client: AMD 3700+ (@ 2.6 ghz), 7800GT

PSU, memory failure, CPU overheat or failure, motherboard failureThe original suggest was indeed good to at least start the process of elimination.. check temps and verify voltages in the hardware monitor. If the 12v is around 11.70-11.75v I would consider a very good possibility the PSU the issue. If its well below that, its definitely the issue.There are times when the voltage can read correctly and the problem is a component in the PSU which reaches a failure temp or point. In some cases the voltage is not tell-taleYou say this reboots and does not shut down so the other possibilities I mentioned are still in the mixThe best way to verify a finicky PSU is to simply put a spare in to test if you have one.If the BIOS shows good voltages and fan speeds/temps then get MEMTEST 86 and run 5 passes in DOS using their boot disk.

PSU is a CoolerMaster 600 Watts eXtreme Power. I have little experience dealing with BIOS. I'm not sure what to do or look for at this point.

I tried this ... I downloaded and installed Speed Fan. I ran the program and this is what it showed:GPU 46CTemp 52CCore 0 75CCore 1 72CCore 2 75CAbout one minute later ...Temp 66CCore 0 91CCore 1 87CCore 2 91CThe Core numbers were nudging the 100s just before I shut the computer down fearing something might be overheating.Do these numbers mean somethings wrong?

Your CPU is overheating.Your heatsink is either loose, or your fan has stopped working.

It is possible that your fans are not getting power...I would open the case with power off, then power on and observe the fan movement. Sounds like either the fans are not working or have become unseated as was said.Do not let the sys run for long if the cpu fan is not turning.RhettFS box: E8500 (@ 3.80 ghz), AC Freezer 7 Pro, ASUS P5E3 Premium, BFG 8800GTX 756 (nVidia 169 WHQL), 4gb DDR3 1600 Patriot Cas7 7-7-7-20 (2T), PC Power 750, WD 150gb 10000rpm Raptor, Seagate 500gb, Silverstone TJ09 case, Vista Ultimate 64ASX Client: AMD 3700+ (@ 2.6 ghz), 7800GT

Thanks guys! Appreciate everyone's thoughts. Take note ... Turns out the pump that circulates the liquid to cool my system has failed. I can see a 3 to 4 inch air gap through the clear line, it isn't moving at all. That explains the overheating and auto shutdowns under moderate to heavy loads. Since my box is just over a year old, I appreciate the 3 year warranty from Cyber Power even more.