You didn't say.
While it's only in 2000 Pro and XP Pro, EFS will do nicely and is widely documented how to backup the credentials in case you move the drive to another machine.
I had downloaded a program several months ago called "Safehouse", which is a hard disk encryption program. It enabled me to encrypt any portion of my hard disk, put files into it and it showed up just as any other hard disk volume. It worked great and was easy to encrypt and decrypt.
Unfortunately, I just installed a new computer and, when I attempted to locate a download for this program, I found no sites available. Also, when I attempted to go to the webste of the developer (PC Dynamics), I received a "Page Not Found" message--the same message when I attempted to locate downlad sites for it.
Does anyone know if they are still in business? Or, alternatively, where can I download this program? Or--is there another seamless, easy to use program for hard disk encryption?