There are several things you can try.
1. Try to lower the core voltage. If it's underclocked the CPU might run
stable with lower core voltage. This saves a lot of heat because power
is proportional to voltage squared.
2. I was amazed how silent a fan is when I hold it in the hand. When
it's mounted to the heatsink most of the noise seems to come from
vibrations passed to the heatsink and board. I put some rubber between
the fan and the heatsink in one machine and it made a difference.
3. With a fan at a lower speed you might still get enough cooling, but
without too much noise. Put a resistor before the fan. I have a P2
[EMAIL PROTECTED] running with less than half the fan speed for a year now without
any problems.
4. Watercooling. There seem to be a few reliable watercooling blocks
availabele ot there. I build my own for one machine. The pump is almost
inaudible.
I don't know if your CPU or bord have a built in thermometer. I know
that Athlons (and probably any other silicon chips) are allowed 90 C
surface temperature.
Robert