Personally I'd make sure to read online reviews of the external drive I want to buy and look for the noise level. It may be something that only irks me, but I find it disturbing when the harddrive spins too loud. I still haven't bought myself one yet, though, mostly because I use my old white iPod as external drive (I've got 20 GB on it and with enabled disk use, 70% of the space are backup files etc.)