We find IBMs the most noisy when new.
Maxtor most noisy when aging
they can get LOUD
Maxtor Liquid bearing pretty quiet and likely to stay so ( they KNOW they had a problem)
The 40 gig WD w 8 meg cache is quiet the 80 and 120s a bit noisier
Seagates seem very quiet these days - the 40 gig with the rubber jacket is very quiet but only 5400 RPM.
Unless you are doing digital audio or video the 5400 rpm are quiet and reliable - that's what I use for backup.
Michael your best route might be the 40 gig WD if you want speed and quiet and 3 year warranty. I mean it is a truly FAST drive.