Hard drive Encryption

If it is windows, the easiest one is the one built into it, the EFS
(encrypted file system) which uses triple-des as the cipher algorithm,
and that is fairly secure.

If the OS is linux, then it is not so simple to do, but from what I have
tried and read, the most secure is a program called loop-aes.
Essentially you boot off a live linux-cd like knoppix and run the
program from there. If you want to have the HD encrypted while booted
into the OS, you have to recompile the kernel to add in some special
options, and make a loopback device that essentially encrypts/decrypts
data to/from the drive, which is no easy task to set up.

Encryption is not like what's in the movies. It's hard to setup, harder
to break, and not very sexy.


source : http://blog.bletchleypark.net/2006/04/hard_drive_encryption.htm
others : http://www.bletchleypark.net/