Best way to encrypt folders that are used often?

[Mark G. Spencer]

I'm wondering if there are any good ways to encrypt folders/directory
trees that are used often?  Some of the products I have found will
encrypt folders, but they can take up to 20 seconds to encrypt each
megabyte on a slower machine.  This would make it relatively painful to
keep encrypting and decrypting the folders that contain large numbers of
files.

Is there a better way to secure a directory tree on a Windows 2000
system?  I want to assume that the current user logged in is NOT
trusted.

Thanks!

Mark