Maybe your PC is overheating.
Do what Lucky Star said and... Look for PC temperature in BIOS.
If it is high, check that its not a problem with your FAN.
Get a better cooling system or take ur pc to service center.
check ur cpu fan..
and if the heatsink is properly fixed of not.
if u stay at a place where temp goes more than 45 degs, make sure ur cabinet is properly placed, away from closed regions.
my cpu recently alarmed when it's temp went well over 60degs! that day delhi was 45 degs!! and i had my cabinet under my table, hardly any airflow! so please take care of that.