I'm assuming you're talking about the fans under the hood, by the radiator.
First, are you sure it's the fans?
They should not come on as soon as you start the car unless you have the A/C on.
If it is the fans, the squealing could be a worn fan bearing.
If it's not the fans, I would check the serpentine belt and all the pulleys. The belt could be loose, or a pulley could be misaligned. a loose belt will make more of a screetching sound especially at take off. A misalignement is typically more of a 'chirping' sound. A simple test with a water bottle can narrow it down for you: spray the belt with the engine on, if the noise goes away/greatly diminish then comes back, you're probably dealing with a misalignement problem; if the noise increases it's probably a loose belt (either a stretched belt or a worn out tensioner).
Here's a video that shows you how to do that test: http://www.youtube.com/watch?v=fPjmBQc2gGQ