My PC Shutdown

From last 4 days i am facing weired problem.My pc shuts down in an instance without any reason.BTW my casing is uncovered so i can see that yellowish green light remains on of the Mother board.And then i have to power off and then power on and pc starts to restart without any problem.
So where could be the problem ?

 

Have you installed any new hardware recently?

 

Could be a power supply issue, or, overheating if the cooling device on any of your internals (video card for example) is getting ready to retire.

 

I'd go with the power supply or the video card as well. Happened to me in the past. I'd start by replacing the power supply for a new unit.

There is an off-chance it could be a driver issue so you may want to check you have the latest drivers in place. Video drivers are a bugger if they get outdated by a Windows update.

 

does it boot up at all, shows the windows/linux/mac logo? Could be a virus or similar?

 

It definitely sounds like a power supply issue. My computer started doing the same thing about a year or two ago, and almost died. My advice it to start backing up all your important data just in case.

 

Almost definitely overheating. Have a look at your temperature monitor in the BIOS. I'll bet that you see the temperature constantly rise until cut off time. Most new motherboards these days include this feature as a fail safe against frying your CPU. Try monitoring the temp in the BIOS (I know... like watching paint dry) and if it IS climbing to a certain point and then shutting off, then try blowing the dust out of the fans (chassis,cpu,video card,etc.). You may find out that you need a new fan.

 

It could be that from a failing power supply. When mine started to play up the power-supply fan began to fail and so wasn't cooling the unit properly which resulted in overheating.

 

True enough, but I see this kind of thing relatively often. When the power supply goes (or is going), you usually see other symptoms along with the sudden shut-off symptom. You might also expect to see missing devices in the device list (often CD-ROM or DVD-ROM drives) or the system has a difficult time booting and hangs on a black screen before you get the Windows boot up screen.

Note to Nokia999: Keep an eye out for other symptoms like that, but checking the temp in the BIOS is something you can do right away. If your computer always seems to shut off at or near a certain temp, then it's probably heat related. You can always blow the dust out of all the fans and see if the problem persists.

 

I have not installed any new device/driver at all.
My pc runs for 3-4 hours easily after restarting.