It's impossible to say what a user has to do when he forgot the password for the encryption program. I've tried to access the website of the developers, but the old domain redirects to something else now. I've also used the Search function on his website and ddcrypt doesn't appear to even exist, therefore no help can be obtained about it.
Go to the installation directory of ddcrypt (typically in Program Files) and look for Help files that might provide details on how to recover the password, although I highly doubt that's even possible.
