I have a PC that randomly turns off, after 5-60 minutes of use. It could be because of the heat, in summer it does this power off thing more often compared to winter. But the PC didn't do this a year ago and it is 3-4 years old. I'm checking the temperature (with HWMonitor) and nothing is above 60-65C, 140-150F).
Is it possible that some sensor could be damaged because of the heat and now it doesn't show anything?
My PC setup:
Intel Core2 Duo E7600
2* Kingstone DDR3 4GB
Asus ENGTS450 DirectCU 1Gb D5
As i said, it used to work perfectly for 2-3 years and i have the same hardware (well, i bought a stronger CPU cooler and +4Gb ram for the 2nd slot). And i still play the same game, use the same OS tho...
..because what you describe is a typical failing PSU. And cheap ones tend to be the first to go. The GTS is a 107W card (~9 amp). Check your PSU's nameplate for the +12V rating.
Of course, do the obvious. Make sure the 24 pin and 4/8 pin MB connection is inserted all the way and the clip is over the tab on the header. If the connection isn't secure, changing temps can cause it to loose contact.