First of all,, are you using SpeedFan?
link
If not I'd HIGHLY recommend it.
Second.. the good news is there are tons of replacement fans out there. I use the coolermaster neon LED fan myself and found it to be much quieter than the stock jet engine.

Sudhian forums have extension coverage on these replacement fans as well, so check them out >
link
Are you overclocking your SN45G?