Recover data with unknown media passphrase

Running SophosSafeGuard6.0.

Encrypting external data transfers.

I have a client that has transferred data to an external hard drive without a full understanding of what Sophos does.  Needless to say, the data is encrypted and our client has no idea what a media passphrase is.  They have also received a new computer recently and the old one does not exist as it's been formatted, cleaned, and sent away.

Is there any way for me to recover the data that was encrypted from an old computer where the user does not remember ever creating a media passphrase?  Also keep in mind that we no longer have the old computer.

Thanks for all of your assistance in this matter.