CPU Fan Error with loud noises

I need an urgent help please! I have installed Windows XP into my PC with ASUS K8V SE Deluxe as motherboard. Everything was working properly until yesterday when the following error was displayed in the computer screen “CPU Fan Error! Press F1 to continue.”
Therefore, I opened the computer chassis, checked the fan and I discovered that its sound is louder compared before.
I pressed F1 as what the message had directed me to do and it worked very fine.
The only thing that I don’t like is it happens every time I started my PC. It makes me feel uncomfortable always.
Is there somebody who can help me in addressing this problem?
Thanks in advance.
