It's so weird.

I've got two HDs here:

One 250 Hitachi 7200. I thought it was too loud for my xbox (seek noises) so I tried a 300GB Hitach 5400rpm. Supposedly this should be a very quiet drive.

Ok, lobbed it in, but what is that..Same seek noises when Avalaunch scans the drive on startup.... (Loud crunching noises -> seek noise)

Anyway, so I put the drive into an external case to try it with my pc. Now the drive is whisper quiet.

What is the deal with this?... It can't be only vibration in the xbox case...

Thanks,
Chris?

could be vibration, could be just different insulators too, could be the way it's mouted in the external case over the xbox

I had the same problem
it's vibration from the bottom of the drive just hitting the base of the plastic
holder, try pulling up on the drive before tighting the 4 screws
if not try pushing down