A lot of people here concerned about CPU temperature – yes they DO get hot! VERY hot and that's normal. Many people also worried about power supplies. Yes, a faulty PS can cause problems but you can check the voltages by going into the system parameters during start up. Some people here seem to have almost rebuilt their computer to solve this shut-down problem! However, it has happened to me a number of times lately and here was my cause and my solutions:
POSSIBLE CAUSE: I was running Advanced System Care, which apparently runs in the background and continuously scrubs the registry for junk files. SOLUTION: I figured it may be screwing up the registry by doing this constantly so I shut down the "automated care" function (just on speculation), effectively shutting down the ASC software. SUSPECTED CAUSE: Lots of junk files and bits and pieces left over from normal use, that is, odd links and rubbish left behind when deleting files and moving things around. SOLUTION: I ran CCleaner to clean up these junk files. My system shut down again this morning and I ran this cleaner utility and it found and deleted 55.3 Megabytes of junk files from the registry. That's a LOT of junk and rubbish that isn't needed and it screws up the registry. CCleaner is a free download – Google for it. I also sometimes use Registry Mechanic which does the same thing but it is a little more thorough. Not free though, but you can download a trial version with limited capabilities and if you are game enough to browse the pirate software ("warez" or "crackz") websites you will usually find a registration code to fully enable the trial copy. I say "game enough" to browse them only because some of them can give you spyware or worse. Just do a thorough virus scan afterwards, just in case. But most of them, even if they are pirate software websites, are clean and reliable. You could also Google for Hijack This!, run it and follow the instructions to have the results assessed on-line. It will detect viruses and other things that shouldn't be on your computer. Many things can cause a shut down yes, power supply, viruses, RAM, etc., but in my case (and it often happens) it was no more than simply junk files and rubbish screwing up the registry and needing to be cleaned out. The registry does get clogged up over time which will slow down your computer, and giving it a good clean out should improve performance. It might just solve the problem for some people here. Good luck!