As far as noise sensitivity goes, I'm probably one of the most if not the most sensitive of members here.
I'm talking about _feeling_ emf's in my temples even when I can't hear any noise!
In that case, depending what you'll use the notebook for, you could consider getting a notebook where you could remove the hard drive and boot from cd or flash drive, such as with knoppix or damn small linux, toram. If from cd, you can then remove the cd after booting.
I don't know which (if any) notebooks will boot from cd if you completely remove the hard drive.
Maybe it's possible to leave the hard drive in the notebook, if it will spin down since it isn't being used under knoppix. There is a boot option, nofstab, which might help.
Also important to keep the fan from running under normal use. Perhaps a Pentium M or maybe an old PIII or PII (or some other low power chip; I'm no expert) and a model which has software available to control the fans. For example, I8kfangui for certain Dell models. Also try for a video card or onboard video which doesn't make too much heat.
Some old notebooks, like my very old PII notebook, don't run the fans under normal use, even without installing fan control software.