Unformat or decrypt? Without the encryption password or a backup of they key you can make when encrypting, you can't get to whatever was encrypted. If you format an encrypted disk, you destroy anything on there fully as you also wipe the encryption key that was used to encrypt it. Any attempt to find data on that disk will fail.
"If the encrypted partitions are still intact, you should be able to mount them from another BitLocker-enabled Windows (specific editions of Vista or 7) with the 48-digit recovery password via the command line tool manage-bde.wsf."