Encrypt volume/folder that's not empty?

[EdP]

I have an external drive that already contains files and folders. What, if anything, can I use to encrypt the whole thing? Barring that, is there software that will allow me to encrypt just a folder (with subfolders) that has data in it?

I own Drivecrypt 5.1.0, but from reading the Help, it appears that a container or volume is formatted by DC during the encryption setup.

Thanks
EdP

[gb63]

Commercial products - DriveCrypt Plus Pack or Jetico Whole Volume Encryption will encrypt in place.

Free - TrueCrypt 6.1a if you have a Vista or later installation (with XP it would delete, clear, and re-format clean. With Vista it can encrypt in place ).