I seemed to have a power surge last spring that fried the pump on my closed system water cooler. I bought a new one, installed it and things seemed fine for about six weeks.
Old System: bought from IBUYPOWER
MSI P7N SLI motherboard
Intel Core2 Quad 6600
IBUYPOWER closed water cooling system
2GB DDR2 RAM
Seagate 500GB SATA HD (replaced the original Hitachi when it died)
nVidia 8800 GT video card
NZXT 800W power supply
Windows Vista 64
My system would run fine for about an hour or so, then start slowing down until you had to shut it off. I took it to a local long-established computer shop who diagnosed bad RAM and replaced one of the sticks. They also reformatted the HD and reinstalled Windows Vista 64. I took the pc home.
The system would run fine for an hour or so, then shut off. No signs of anything overheating. I took it back to the computer shop who diagnosed a bad power supply and replaced it. I took the pc home.
The system would run fine for about 20 mins or so, then shut off. No signs of anything overheating. I decided perhaps the power surge had damaged something else and purchased new components.
When you're able too, go to start>control panel>adminsitrative tools> Event viewer. Under the windows logs fine application and system logs. looking for the red x's icons. If there are a ton of HDD timeouts it may be a bad HDD. Also, double check how much Memory windows is seeing.