|How is it not working? Making noise, doesnt spin at all, what?|
Most fans can be replaced and will need to be if they are not working because of dirt and dust trapped inside them. If it is simply not getting any power it might be easily fixed by plugging the fans connector back into the motherboard, or if that's not the case it might be a sign of a bigger problem.
If your fan needs to be replaced and you know someone who can replace it for you it can be a cheap fix. If you dont you may need to take it to a shop. Find a good one by askign around.