It sounds like a fan is running when the car is on... on 2009 Lexus ES350

Today, 6/18/12, when I started my car I heard this loud noise coming from under the hood. It never stopped the entire trip to work. Has anyone had this occur? BTW It never ran hot. Do you think it's harming the engine? Thx. (No codes showed up on the screen.) it did it again on the drive home.

Asked by for the 2009 Lexus ES350