NEW READERS START HERE (click) tells you everything you need to know, but to summarise:
The standard FTP server provides access ONLY to the internal drive, and is ONLY useful to archive recordings and then return them TO THE SAME DEVICE because the encryption is locked to your particular box. StDef recordings are decrypted if you copy them to a USB drive and then walk them to your PC, HiDef recordings can be decrypted if you unlock them first (for which you have to FTP the .hmt file to PC and run Foxy on it, then FTP it back) but note that you are limited to 4GB max with a FAT32 drive and the Humax won't write to a NTFS drive.
You can use streaming to send StDef recordings DECRYPTED across the network and save to PC, using instructions
HERE (click).
Your options become much wider if you install the custom software. You will be able to unlock HiDef recordings automatically, download decrypted StDef or HiDef recordings directly through the web interface, edit recordings directly on the Humax, decrypt files on the drive, control your recording schedule away from home (via Internet)... the list is almost endless.