usually just your fan belts or air-conditioning belt that needs tightening. If it is loose, (easy to check stopped engine! is there too much give in the belt?. ) it is fairly easy to tighten.If it isn't the belts, then as the gentleman said below you have a more serious question. But if it is the belt and you don't fix it, then very soon the belt will be worn through and you need a new belt installed -- even more expensive.