Before you tear it out, first rule out that it might be loose?
How loud is the hum, could it be that it is loose, causing vibration between it and the cabinet?
Or is it really loud, like something wrong inside of it?
Any grinding or rattling type of noises?
might be good to shop around for a new one, imo. Just in case.
While it is still functioning, a complete transfer of everything is possible, with no data loss. Most new hard drives come with an install disk, where
you can specify that the new drive is to replace the old one, and everything will be duplicated to the new drive, including the Operating System
Instructions to do that vary from manufaturer to manufacturer, but are very similar.
But if you wait until it is too late, than all will be potentially lost.
So depending on your budget, I would strongly suggest looking for a new one, if it is indeed going "south".
The worst that can happen if the drive is not dying, is you have assured yourself with a new drive, and can use the old one as temporary backup
storage. And rest easy in knowing that your boot drive(with the OS on it) is in tip top shape.
but as always, I recommend that you get a second opinion as well.
[edit on 2/23/2007 by Mechanic 32]