how do u fix it i dont know how to take the power supply off
DO NOT ATTEMPT TO REPLACE THE FAN IN THE POWER SUPPLY!
You need to buy a new power supply. Do not attempt to replace the fan yourself.
I agree with eldmannen.(wow first time in a while )
Decent PSUs arent very expensive and too much could go wrong with a bad one.
Just order one off newegg:
http://www.newegg.com/Product/ProductList....;SubCategory=58
Just out of curiosity, are you on a 'gaming' computer or just a regular, browse -the-internet-sync-some-pictures kind of computer? If you're gaming, you will probably need a 450W+ PSU, while for more casual computers, a 300-350W should be fine.