Building a small HTPC for a friend and with passive cooling except for two Nexus 80 mm fans. We choose a 5400 2.5" drive but we realize that the case lacks HDD dampening and acoustics are really important.

Anyone got an idea for dampening the drive? Been considering soft silicone for normal use in bathrooms but none seems to have tried it before.

I would not bother really. My 2.5" WD Scorpio Blue in my Antec ISK-300 65 did not produce any vibration noise in the past 18 months. The fan that came with the case was to only annoying thing about the case... but my layaround 80mm Panaflo L1A's sorted that out

I have a 7200rpm Samsung in mine and it doesn't cause any vibrations. I can of course hear the disk spinning (being a 7200), but nothing actually transferred to the chassis.

As for ideas: there are two brown pieces of stiff paper that come with the case that I believe you are supposed to sandwich between the drive and the mounts. I don't think these are actually useful, but you could use it as a template to drill holes so that you could move the HDD over a bit. You could then use some [thin] soft rubber grommets to decouple the drive from the mount, and then maybe stick a piece of foam on top of the drive just in case the top of the chassis touches it. Any vibrations would then be absorbed.

The reason you would have to move it over is because there is a lip that goes over the edge of the HDD. I guess the lip could be dremeled, but the other way would probably be cleaner and easier.

These are a couple of things I thought about doing before I actually installed everything. After getting everything running, I realized that there wasn't really a point since it was quiet enough (and yes, I am actually pretty sensitive to noise).

Hope this helps.