dOES THE COOLING FAN TURN ON AND OFF INTERMITTENLY AS THE CPU HEATSUP? MY DAD HAS A RELATIVELY NEW COMPUTER THAT SHUTS DOWN AFTER IT BEEN ON FOR A WHILE, I OPENED IT AND LOOKED FOR DUST - NONE TO SPEAK OF AND TO MAKE SURE THE CPU FAN WAS WORKING, IT DOES BUT TURNS ON AND OFF EVER FEW MINUTES?