cpu shutting down i believe due to over heating

i have had trouble with my cpu shutting down i believe due to over heating

cleaned it
did virus check thought it might me a software issue

I never get an error

my buddy is a TECH he said to elevate it of the carpet so I did

Fans are running but they are like supper quiet they were like supper loud before


I take very good care of my CPU

i I have 3 fans they are all running

ACER M5100 QUADCORE 4GB RAM

Windows Vista 32

Is quiet, good or bad!

could someone help me out?

Thanx

J