if you search the form, this has been discussed over, and over, and over, and over, and over again. Basically tons of people on here have had their harddrives go through hell, and have had no problems. I've driven on 10 miles of gravel road with my system right near the sub, no problems. People have been in accidents, their computer still running solid...etc. My hdd does have shock absorbant mounts, but their main purpose if to limin vibration noise between the hdd and the cooling bracket I have on there. The mounts came with my hdd mount.
Pic of the mounts
the hdd cooler itself