there is no encryption that cannot be un-encrypted...
especially on standard commercial hard drives. w/ standard commercial operating systems.
I suppose that's true, but if it takes longer than the age of the universe with computers that don't even exist yet to decrypt the information, I would think you are safe.
There is a sculpture called Kryptos by artist Jim Sanborn in front of the CIA building with a code embedded in it that no one in the CIA has been able to crack for almost 20 years.