Encrypt your data with TrueCrypt. TrueCrypt is a free open-source encryption program.
It creates a virtual encrypted disk in a file and mounts it as a real disk. It encrypts partitions, USB drives, and external hard drives as well. The main thing I liked about it is that it has two levels of plausible deniability just in case you are forced to give up a password. TrueCrypt is supported on Windows Vista, Windows Xp, Mac OS X, and Linux.
Download:TrueCrypt
