How can I encrypt a USB drive and still be able to open it?

How can I encrypt a USB drive and still be able to open it?
[Q]
I would like to use an encryption program to encrypt all of the files on my USB drive, but still be able to open it no matter where I go, even if the computer I am using the USB on does not have the encryption program. Is there a way for me to encrypt my USB drive so that when I plug it into a computer, it asks me for my password to unencrypt regardless of whether or not the computer has an encrypting program?
[A]
Why don’t you use GiliSoft Private Disk or GiliSoft USB Stick Encryption to encrypt your USB drive?