Agreed, what system do you have. If you don't know the cpu, you can download free software, called cpuz, that will tell you what brand and model number your cpu is.
How old is the system, is it possible that dust is clogging either your fan or your heatsink below your fan, which effectively prevents cpu cooling? If so, forcing air with a vacuum or compressed tank is the best way to clear these out.
Is it possible that a wire on your motherboard is preventing your heatsink fan from spinning? I have seen this before.
The more details you can provide us about your system, including age, and if it is prebuilt at a factory, like a dell or hp, the better.
Is this system built yourself? How did you apply thermal paste to the processor? Ideally, you should apply a layer thin enough that you can almost see through it.
It was my first inter-action with any PC hardware forum...and i really found very-2 useful .
My all friends helped me a lot to counter my problem...i have just cleaned dust from main-board...heat-sink connection to board....cpu cooler fan..and my major sudden-shut-down problem has gone..with controling high-temp..but over-heating is till there...65-80 degrees...so.. now I am planning to add much better cooling facilties to my system unit..as re-appliying thermal paste...increasing cpu cooler fan speed..addind more fans ..for better air fow ..purchase a comprssed air tank to clean up all dust.....it will work.... I am 200% sure....thanx once again to my dear friends....Pawan Verma....Rajasthan ----India....