help with external hdd and post your setup

Hi all,
I just got my new OWC mercury elite 320 GB external harddrive. it looks beautiful, came with usb, fw400, and fw800 cords. the only downfall is that it vibrates a lot. It is ultra quiet, but the thing seems to add vibration to the entire desk. anyways, i created two partitions on it. One for a system backup (about 90GB) and another to just store files on it and such. Not sure if im going to run my itunes music from it yet or not because i kindof like it on my computer and i still have around 40GB free on my internal.

My question is: is there any way to not have the bootable partition mount and also, why does my computer seem slower when the hdd is mounted or is it just me?

any of you out there want to share you external hdd experiences and setup and perhaps give me some tips.

Thanks a lot.