I've read about this Novibes thing. The online store where I got some of my other silencing products also sells it.

Actually, it gave me an idea. Yesterday I packed the insides of my PC in with sound-damping mats, also in the spirit of killing as much noise as possible. These sound damping mats are made of a soft carpet-like material and get glued onto the iron of the case. (on the inside)

So I figured I'd remove my HD's from the hd rack of the PC and just lay them onto the 'carpet' on the bottom of the case.

Result? AMAZING! A whisper-quiet PC! Incredible!

This would be ideal, but I don't think I'll keep it this way. For one, there's an 80mm fan on the back of that drive bay containing my two hd's that actively cools them (I believe this is necessary for 7200RPM drives.) If I lay my Hd's on the bottom of my PC case I can't use that fan anymore to cool them. I don't like that very much.

Though that Nvibes option sounds great, I think it's a pity it requires a 5,25" drive bay. I've got two HD's in that case, and only one 5,25" slot free. (of course)...

However, the difference in sound level is just too big to ignore. I'll see if I can manually mod my case somwhat to allow me to use it in this fashion AND keep the HD's adequately cooled. This should be do-able.
I'll look into this next week. I don't have the time for it this week.