
If you are the owner of a power Mac from august 2002, don't hesitate to order the exchange kit from Apple including a new power supply and a 12 cm fan. You should install it yourself which takes roughly 45 mn (as I experience it). It's not really complicated, just take your time.
The difference in terms of noise is striking, no more high frequencies noise but instead, a normal low background noise. It costs approximately $24 $ which is quite reasonable for the service.
So just go for it, and remember that thoses are the lastest machines able to boot under OS 9: with a new power supply their value for future selling will only increase!