there is probably nothing wrong with the hard drive.
some hard drives are nosier than others.
hard drives are like car tires: you just don't know when they're gonna blow
noises may be a sign that a hard drive is failing, but they typically don't get noisy right before they go, they just go.
if you can be without it for a while then taking it in may not be a bad idea, i guess
but the person who recommended an external hard drive is on track...backups are always a good idea