unfortunately such a noise usually means something is wrong with the drive bearings.
they may just be very loud due to being unbalanced, or it may be a sign that your drive is soon to die. just to be safe i reccomend you backup all your important data.
as for what you can do... very little.
you can try to mount the drive on rubber shock adsorbing things to dampen vibrations, but thats unlikely to do much unles the drive is loose.
apart from that, the only way to fix it is to replace the drive.
<b>Trust Me, Trust Yourself, Trust the Hamster. Anyone else - Shoot Them.
</b> This sig was proudly brought to you by <i>Hammie</i>