I don't have much of a point of reference here. I have a couple of old 1.2Gb Maxtors kicking around and they fairly rattle when they read and write. I wouldn't worry too much about it if the drive works OK, unless it makes inordinate amounts of noise while it's sitting there just spinning, not actually accessing the disk.
Hmm - just to add to that - if you get a lot of noise, it's possible that it has something to do with the way the drive (or something else) is mounted, rather than having anything innately to do with the drive. Does the drive still make this much noise if you take it out of the bracket? (Btw, don't do this if you're not confident messing with the guts of your PC!) I remember I once stupidly mounted a hard disk in such a way that the front of the drive was touching the front of the case; it rattled like hell and worried me until I figured out what I'd done.
- Freon
