P5ND2-SLI (not Delux) CPU Fan Speed Question

Have this board and have been pretty happy with it for about a year
now. However, one thing I have never liked is the fan noise from CPU.

It appears in reading that as I did not get the 'delux' edition Asus
isn't going to help me get the fan speed down. I have barrowed and
used a manual gaget to reduce rotation speed. I can get the fan down
to levels that are very quiet and the CPU temps are fine

So the question is, does anyone know any tricks (short of buying a
$40-90 aftermarket fan) to get my non-delux board via AI Booster or
something else to lower rotational speed of CPU way down

Thanks