CPU Fan turn mad at power on

As I said from last few days my CPU fan sound noisy when I turn on the power button after few secs its come back to normal I have Dell OPTIPLEX 760 model Core 2 duo 3.2Ghz 4gb ram what should I do back to normal ?
Answer #1
Clean it and see how you get on.
I somewhat remember when I powered on my dell desktop, the cpu fan would go REALLY fast for a few scones and back to normal.
If your cpu cooler is dust free, you’ve got nothing to worry about.
Answer #2
Check in the bios if your temperature is normal..
If it is then look in the bios..There is an option to control the cpu fan..Change it from Auto to disable..
Answer #3
i think it not cpu fan, it psu fan, they dry out
Answer #4
Slap in a custom socket LGA 775 cooler and be done with it. A little clean wouldn’t hurt too, a can of compressed air and take the pos outside to do it.