Is there good encryption software for external or portable hard drives.
TrueCrypt, its free.
if you have vista ultimate- it's built in. If you have XP or other flavors of vista, there are dozens of encryption programs. Go to a good open source site like sourceforge.net
remember that if the external device goes travelling (eg a thumbdrive), then any
system to which you attach it will need the same software OR
a compatible decryption capability.
OpenPGP is also available for various platforms, eg Linux, Mac, PCs