Possible Duplicate:
What software should I use to encrypt my hard drive?
Hi,
What is the easiest/most secure way of encrypting folders on my external HD or laptop ?
Possible Duplicate:
What software should I use to encrypt my hard drive?
Hi,
What is the easiest/most secure way of encrypting folders on my external HD or laptop ?
Use a truecrypt container.
It creates a file that acts as hard disk image, and it's encrypted with truecrypt.
As for your external drive, you could encrypt that all together.
Mac OS X includes Disk Utility, which can be used to create an encrypted image or sparse image.
If you've got Windows 7 Ultimate or Enterprise, you can use BitLocker to go, which "gives the lockdown treatment to easily-misplaced portable storage devices like USB flash drives and external hard drives."